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feat(skills): Add n8n-automation collection (3 skill sets, 14 files)

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- expression-syntax: {{}} expressions, ,  variables
- javascript-code: Code nodes, , , patterns
- node-configuration: Operation-aware setup, dependencies
- n8n runs on Command Center for Firefrost workflows
- Updated SKILLS-INDEX.md

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---
### n8n-automation (collection)
**Location:** `docs/skills/n8n-automation/`
**Source:** skill.fish
**Triggers:** n8n, workflow automation, expressions, Code node, JavaScript, node configuration
**Purpose:** n8n workflow automation guidance
**What It Covers:**
- **expression-syntax/** — {{}} expressions, $json, $node, $now variables
- **javascript-code/** — Code nodes, $input, $helpers, DateTime
- **node-configuration/** — Operation-aware node setup, property dependencies
**Firefrost Context:**
- n8n runs on Command Center (63.143.34.217)
- Used for: Subscription sync, server monitoring, notifications
**Read This When:**
- Writing n8n expressions
- Creating Code nodes with JavaScript
- Configuring complex nodes
- Troubleshooting n8n errors
---
### postgres-patterns
**Location:** `docs/skills/postgres-patterns/SKILL.md`
**Source:** skill.fish (affaan-m/everything-claude-code)
@@ -454,6 +478,22 @@ docs/skills/
│ └── SKILL.md
├── minecraft-mod-dev/
│ └── SKILL.md
├── n8n-automation/
│ ├── README.md
│ ├── expression-syntax/
│ │ ├── SKILL.md
│ │ ├── EXAMPLES.md
│ │ └── COMMON_MISTAKES.md
│ ├── javascript-code/
│ │ ├── SKILL.md
│ │ ├── DATA_ACCESS.md
│ │ ├── BUILTIN_FUNCTIONS.md
│ │ ├── COMMON_PATTERNS.md
│ │ └── ERROR_PATTERNS.md
│ └── node-configuration/
│ ├── SKILL.md
│ ├── OPERATION_PATTERNS.md
│ └── DEPENDENCIES.md
├── postgres-patterns/
│ └── SKILL.md
├── social-automation/

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# n8n Automation Skills
Comprehensive n8n workflow automation guidance for Firefrost.
**n8n Location:** Command Center (63.143.34.217)
**Access:** https://n8n.firefrostgaming.com (or via Cloudflare tunnel)
---
## Available Skills
| Skill | Folder | Purpose |
|-------|--------|---------|
| Expression Syntax | `expression-syntax/` | {{}} expressions, $json, $node variables |
| JavaScript Code | `javascript-code/` | Code nodes, $input, $helpers |
| Node Configuration | `node-configuration/` | Operation-aware node setup |
---
## Quick Reference
### Expression Syntax (expression-syntax/)
```javascript
// Access current node data
{{$json.fieldName}}
{{$json.body.email}} // Webhook data is under .body!
// Access other nodes
{{$node["HTTP Request"].json.data}}
// Dates
{{$now.toFormat('yyyy-MM-dd')}}
```
**Files:**
- `SKILL.md` — Core syntax guide
- `EXAMPLES.md` — Common expression examples
- `COMMON_MISTAKES.md` — Pitfalls to avoid
---
### JavaScript Code (javascript-code/)
```javascript
// Basic Code node template
const items = $input.all();
const processed = items.map(item => ({
json: {
...item.json,
processed: true
}
}));
return processed; // MUST return [{json: {...}}] format
```
**Files:**
- `SKILL.md` — Core guidance
- `DATA_ACCESS.md` — $input, $json patterns
- `BUILTIN_FUNCTIONS.md` — $helpers.httpRequest(), DateTime
- `COMMON_PATTERNS.md` — Reusable code snippets
- `ERROR_PATTERNS.md` — Debugging help
---
### Node Configuration (node-configuration/)
**Philosophy:** Progressive disclosure — start minimal, add complexity
1. **get_node_essentials** — Use first (91.7% success rate)
2. **get_property_dependencies** — For complex nodes
3. **get_node_info** — Full schema when needed
**Files:**
- `SKILL.md` — Core concepts
- `OPERATION_PATTERNS.md` — Node-specific patterns
- `DEPENDENCIES.md` — Property dependency chains
---
## Firefrost n8n Use Cases
| Workflow | Description |
|----------|-------------|
| Subscription sync | Stripe → Discord role assignment |
| Server monitoring | Pterodactyl → Discord alerts |
| Backup notifications | Server backup status → Discord |
| Welcome automation | New subscriber → Welcome email/DM |
---
## Common Pitfalls
1. **Webhook data location:** Data is in `$json.body`, not `$json` directly
2. **Return format:** Code nodes MUST return `[{json: {...}}]`
3. **Node names:** Case-sensitive, must match exactly
4. **Expression braces:** Use `{{}}` not `{}`
---
**Source:** skill.fish
**Added:** 2026-04-09 by Chronicler #73
**Fire + Frost + Foundation = Where Love Builds Legacy** 💙🔥❄️

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# Common n8n Expression Mistakes
Complete catalog of expression errors with explanations and fixes.
---
## 1. Missing Curly Braces
**Problem**: Expression not recognized, shows as literal text
❌ **Wrong**:
```
$json.email
```
✅ **Correct**:
```
{{$json.email}}
```
**Why it fails**: n8n treats text without {{ }} as a literal string. Expressions must be wrapped to be evaluated.
**How to identify**: Field shows exact text like "$json.email" instead of actual value.
---
## 2. Webhook Body Access
**Problem**: Undefined values when accessing webhook data
❌ **Wrong**:
```
{{$json.name}}
{{$json.email}}
{{$json.message}}
```
✅ **Correct**:
```
{{$json.body.name}}
{{$json.body.email}}
{{$json.body.message}}
```
**Why it fails**: Webhook node wraps incoming data under `.body` property. The root `$json` contains headers, params, query, and body.
**Webhook structure**:
```javascript
{
"headers": {...},
"params": {...},
"query": {...},
"body": { // User data is HERE!
"name": "John",
"email": "john@example.com"
}
}
```
**How to identify**: Webhook workflow shows "undefined" for fields that are definitely being sent.
---
## 3. Spaces in Field Names
**Problem**: Syntax error or undefined value
❌ **Wrong**:
```
{{$json.first name}}
{{$json.user data.email}}
```
✅ **Correct**:
```
{{$json['first name']}}
{{$json['user data'].email}}
```
**Why it fails**: Spaces break dot notation. JavaScript interprets space as end of property name.
**How to identify**: Error message about unexpected token, or undefined when field exists.
---
## 4. Spaces in Node Names
**Problem**: Cannot access other node's data
❌ **Wrong**:
```
{{$node.HTTP Request.json.data}}
{{$node.Respond to Webhook.json}}
```
✅ **Correct**:
```
{{$node["HTTP Request"].json.data}}
{{$node["Respond to Webhook"].json}}
```
**Why it fails**: Node names are treated as object property names and need quotes when they contain spaces.
**How to identify**: Error like "Cannot read property 'Request' of undefined"
---
## 5. Incorrect Node Reference Case
**Problem**: Undefined or wrong data returned
❌ **Wrong**:
```
{{$node["http request"].json.data}} // lowercase
{{$node["Http Request"].json.data}} // wrong capitalization
```
✅ **Correct**:
```
{{$node["HTTP Request"].json.data}} // exact match
```
**Why it fails**: Node names are **case-sensitive**. Must match exactly as shown in workflow.
**How to identify**: Undefined value even though node exists and has data.
---
## 6. Double Wrapping
**Problem**: Literal {{ }} appears in output
❌ **Wrong**:
```
{{{$json.field}}}
```
✅ **Correct**:
```
{{$json.field}}
```
**Why it fails**: Only one set of {{ }} is needed. Extra braces are treated as literal characters.
**How to identify**: Output shows "{{value}}" instead of just "value".
---
## 7. Array Access with Dots
**Problem**: Syntax error or undefined
❌ **Wrong**:
```
{{$json.items.0.name}}
{{$json.users.1.email}}
```
✅ **Correct**:
```
{{$json.items[0].name}}
{{$json.users[1].email}}
```
**Why it fails**: Array indices require brackets, not dots. Number after dot is invalid JavaScript.
**How to identify**: Syntax error or "Cannot read property '0' of undefined"
---
## 8. Using Expressions in Code Nodes
**Problem**: Literal string instead of value, or errors
❌ **Wrong (in Code node)**:
```javascript
const email = '{{$json.email}}';
const name = '={{$json.body.name}}';
```
✅ **Correct (in Code node)**:
```javascript
const email = $json.email;
const name = $json.body.name;
// Or using Code node API
const email = $input.item.json.email;
const allItems = $input.all();
```
**Why it fails**: Code nodes have **direct access** to data. The {{ }} syntax is for expression fields in other nodes, not for JavaScript code.
**How to identify**: Literal string "{{$json.email}}" appears in Code node output instead of actual value.
---
## 9. Missing Quotes in $node Reference
**Problem**: Syntax error
❌ **Wrong**:
```
{{$node[HTTP Request].json.data}}
```
✅ **Correct**:
```
{{$node["HTTP Request"].json.data}}
```
**Why it fails**: Node names must be quoted strings inside brackets.
**How to identify**: Syntax error "Unexpected identifier"
---
## 10. Incorrect Property Path
**Problem**: Undefined value
❌ **Wrong**:
```
{{$json.data.items.name}} // items is an array
{{$json.user.email}} // user doesn't exist, it's userData
```
✅ **Correct**:
```
{{$json.data.items[0].name}} // access array element
{{$json.userData.email}} // correct property name
```
**Why it fails**: Wrong path to data. Arrays need index, property names must be exact.
**How to identify**: Check actual data structure using expression editor preview.
---
## 11. Using = Prefix Outside JSON
**Problem**: Literal "=" appears in output
❌ **Wrong (in text field)**:
```
Email: ={{$json.email}}
```
✅ **Correct (in text field)**:
```
Email: {{$json.email}}
```
**Note**: The `=` prefix is **only** needed in JSON mode or when you want to set entire field value to expression result:
```javascript
// JSON mode (set property to expression)
{
"email": "={{$json.body.email}}"
}
// Text mode (no = needed)
Hello {{$json.body.name}}!
```
**Why it fails**: The `=` is parsed as literal text in non-JSON contexts.
**How to identify**: Output shows "=john@example.com" instead of "john@example.com"
---
## 12. Expressions in Webhook Path
**Problem**: Path doesn't update, validation error
❌ **Wrong**:
```
path: "{{$json.user_id}}/webhook"
path: "users/={{$env.TENANT_ID}}"
```
✅ **Correct**:
```
path: "my-webhook" // Static paths only
path: "user-webhook/:userId" // Use dynamic URL parameters instead
```
**Why it fails**: Webhook paths must be static. Use dynamic URL parameters (`:paramName`) instead of expressions.
**How to identify**: Webhook path doesn't change or validation warns about invalid path.
---
## 13. Forgetting .json in $node Reference
**Problem**: Undefined or wrong data
❌ **Wrong**:
```
{{$node["HTTP Request"].data}} // Missing .json
{{$node["Webhook"].body.email}} // Missing .json
```
✅ **Correct**:
```
{{$node["HTTP Request"].json.data}}
{{$node["Webhook"].json.body.email}}
```
**Why it fails**: Node data is always under `.json` property (or `.binary` for binary data).
**How to identify**: Undefined value when you know the node has data.
---
## 14. String Concatenation Confusion
**Problem**: Attempting JavaScript template literals
❌ **Wrong**:
```
`Hello ${$json.name}!` // Template literal syntax
"Hello " + $json.name + "!" // String concatenation
```
✅ **Correct**:
```
Hello {{$json.name}}! // n8n expressions auto-concatenate
```
**Why it fails**: n8n expressions don't use JavaScript template literal syntax. Adjacent text and expressions are automatically concatenated.
**How to identify**: Literal backticks or + symbols appear in output.
---
## 15. Empty Expression Brackets
**Problem**: Literal {{}} in output
❌ **Wrong**:
```
{{}}
{{ }}
```
✅ **Correct**:
```
{{$json.field}} // Include expression content
```
**Why it fails**: Empty expression brackets have nothing to evaluate.
**How to identify**: Literal "{{ }}" text appears in output.
---
## Quick Reference Table
| Error | Symptom | Fix |
|-------|---------|-----|
| No {{ }} | Literal text | Add {{ }} |
| Webhook data | Undefined | Add `.body` |
| Space in field | Syntax error | Use `['field name']` |
| Space in node | Undefined | Use `["Node Name"]` |
| Wrong case | Undefined | Match exact case |
| Double {{ }} | Literal braces | Remove extra {{ }} |
| .0 array | Syntax error | Use [0] |
| {{ }} in Code | Literal string | Remove {{ }} |
| No quotes in $node | Syntax error | Add quotes |
| Wrong path | Undefined | Check data structure |
| = in text | Literal = | Remove = prefix |
| Dynamic path | Doesn't work | Use static path |
| Missing .json | Undefined | Add .json |
| Template literals | Literal text | Use {{ }} |
| Empty {{ }} | Literal braces | Add expression |
---
## Debugging Process
When expression doesn't work:
1. **Check braces**: Is it wrapped in {{ }}?
2. **Check data source**: Is it webhook data? Add `.body`
3. **Check spaces**: Field or node name has spaces? Use brackets
4. **Check case**: Does node name match exactly?
5. **Check path**: Is the property path correct?
6. **Use expression editor**: Preview shows actual result
7. **Check context**: Is it a Code node? Remove {{ }}
---
**Related**: See [EXAMPLES.md](EXAMPLES.md) for working examples of correct syntax.

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# n8n Expression Examples
Real working examples from n8n workflows.
---
## Example 1: Webhook Form Submission
**Scenario**: Form submission webhook posts to Slack
**Workflow**: Webhook → Slack
**Webhook Input** (POST):
```json
{
"name": "John Doe",
"email": "john@example.com",
"company": "Acme Corp",
"message": "Interested in your product"
}
```
**Webhook Node Output**:
```json
{
"headers": {"content-type": "application/json"},
"params": {},
"query": {},
"body": {
"name": "John Doe",
"email": "john@example.com",
"company": "Acme Corp",
"message": "Interested in your product"
}
}
```
**In Slack Node** (text field):
```
New form submission! 📝
Name: {{$json.body.name}}
Email: {{$json.body.email}}
Company: {{$json.body.company}}
Message: {{$json.body.message}}
```
**Output**:
```
New form submission! 📝
Name: John Doe
Email: john@example.com
Company: Acme Corp
Message: Interested in your product
```
---
## Example 2: HTTP API to Database
**Scenario**: Fetch user data from API and insert into database
**Workflow**: Schedule → HTTP Request → Postgres
**HTTP Request Returns**:
```json
{
"data": {
"users": [
{
"id": 123,
"name": "Alice Smith",
"email": "alice@example.com",
"role": "admin"
}
]
}
}
```
**In Postgres Node** (INSERT statement):
```sql
INSERT INTO users (user_id, name, email, role, synced_at)
VALUES (
{{$json.data.users[0].id}},
'{{$json.data.users[0].name}}',
'{{$json.data.users[0].email}}',
'{{$json.data.users[0].role}}',
'{{$now.toFormat('yyyy-MM-dd HH:mm:ss')}}'
)
```
**Result**: User inserted with current timestamp
---
## Example 3: Multi-Node Data Flow
**Scenario**: Webhook → HTTP Request → Email
**Workflow Structure**:
1. Webhook receives order ID
2. HTTP Request fetches order details
3. Email sends confirmation
### Node 1: Webhook
**Receives**:
```json
{
"body": {
"order_id": "ORD-12345"
}
}
```
### Node 2: HTTP Request
**URL field**:
```
https://api.example.com/orders/{{$json.body.order_id}}
```
**Returns**:
```json
{
"order": {
"id": "ORD-12345",
"customer": "Bob Jones",
"total": 99.99,
"items": ["Widget", "Gadget"]
}
}
```
### Node 3: Email
**Subject**:
```
Order {{$node["Webhook"].json.body.order_id}} Confirmed
```
**Body**:
```
Dear {{$node["HTTP Request"].json.order.customer}},
Your order {{$node["Webhook"].json.body.order_id}} has been confirmed!
Total: ${{$node["HTTP Request"].json.order.total}}
Items: {{$node["HTTP Request"].json.order.items.join(', ')}}
Thank you for your purchase!
```
**Email Result**:
```
Subject: Order ORD-12345 Confirmed
Dear Bob Jones,
Your order ORD-12345 has been confirmed!
Total: $99.99
Items: Widget, Gadget
Thank you for your purchase!
```
---
## Example 4: Date Formatting
**Scenario**: Various date format outputs
**Current Time**: 2025-10-20 14:30:45
### ISO Format
```javascript
{{$now.toISO()}}
```
**Output**: `2025-10-20T14:30:45.000Z`
### Custom Date Format
```javascript
{{$now.toFormat('yyyy-MM-dd')}}
```
**Output**: `2025-10-20`
### Time Only
```javascript
{{$now.toFormat('HH:mm:ss')}}
```
**Output**: `14:30:45`
### Full Readable Format
```javascript
{{$now.toFormat('MMMM dd, yyyy')}}
```
**Output**: `October 20, 2025`
### Date Math - Future
```javascript
{{$now.plus({days: 7}).toFormat('yyyy-MM-dd')}}
```
**Output**: `2025-10-27`
### Date Math - Past
```javascript
{{$now.minus({hours: 24}).toFormat('yyyy-MM-dd HH:mm')}}
```
**Output**: `2025-10-19 14:30`
---
## Example 5: Array Operations
**Data**:
```json
{
"users": [
{"name": "Alice", "email": "alice@example.com"},
{"name": "Bob", "email": "bob@example.com"},
{"name": "Charlie", "email": "charlie@example.com"}
]
}
```
### First User
```javascript
{{$json.users[0].name}}
```
**Output**: `Alice`
### Last User
```javascript
{{$json.users[$json.users.length - 1].name}}
```
**Output**: `Charlie`
### All Emails (Join)
```javascript
{{$json.users.map(u => u.email).join(', ')}}
```
**Output**: `alice@example.com, bob@example.com, charlie@example.com`
### Array Length
```javascript
{{$json.users.length}}
```
**Output**: `3`
---
## Example 6: Conditional Logic
**Data**:
```json
{
"order": {
"status": "completed",
"total": 150
}
}
```
### Ternary Operator
```javascript
{{$json.order.status === 'completed' ? 'Order Complete ✓' : 'Pending...'}}
```
**Output**: `Order Complete ✓`
### Default Values
```javascript
{{$json.order.notes || 'No notes provided'}}
```
**Output**: `No notes provided` (if notes field doesn't exist)
### Multiple Conditions
```javascript
{{$json.order.total > 100 ? 'Premium Customer' : 'Standard Customer'}}
```
**Output**: `Premium Customer`
---
## Example 7: String Manipulation
**Data**:
```json
{
"user": {
"email": "JOHN@EXAMPLE.COM",
"message": " Hello World "
}
}
```
### Lowercase
```javascript
{{$json.user.email.toLowerCase()}}
```
**Output**: `john@example.com`
### Uppercase
```javascript
{{$json.user.message.toUpperCase()}}
```
**Output**: ` HELLO WORLD `
### Trim
```javascript
{{$json.user.message.trim()}}
```
**Output**: `Hello World`
### Substring
```javascript
{{$json.user.email.substring(0, 4)}}
```
**Output**: `JOHN`
### Replace
```javascript
{{$json.user.message.replace('World', 'n8n')}}
```
**Output**: ` Hello n8n `
---
## Example 8: Fields with Spaces
**Data**:
```json
{
"user data": {
"first name": "Jane",
"last name": "Doe",
"phone number": "+1234567890"
}
}
```
### Bracket Notation
```javascript
{{$json['user data']['first name']}}
```
**Output**: `Jane`
### Combined
```javascript
{{$json['user data']['first name']}} {{$json['user data']['last name']}}
```
**Output**: `Jane Doe`
### Nested Spaces
```javascript
Contact: {{$json['user data']['phone number']}}
```
**Output**: `Contact: +1234567890`
---
## Example 9: Code Node (Direct Access)
**Code Node**: Transform webhook data
**Input** (from Webhook node):
```json
{
"body": {
"items": ["apple", "banana", "cherry"]
}
}
```
**Code** (JavaScript):
```javascript
// ✅ Direct access (no {{ }})
const items = $json.body.items;
// Transform to uppercase
const uppercased = items.map(item => item.toUpperCase());
// Return in n8n format
return [{
json: {
original: items,
transformed: uppercased,
count: items.length
}
}];
```
**Output**:
```json
{
"original": ["apple", "banana", "cherry"],
"transformed": ["APPLE", "BANANA", "CHERRY"],
"count": 3
}
```
---
## Example 10: Environment Variables
**Setup**: Environment variable `API_KEY=secret123`
### In HTTP Request (Headers)
```javascript
Authorization: Bearer {{$env.API_KEY}}
```
**Result**: `Authorization: Bearer secret123`
### In URL
```javascript
https://api.example.com/data?key={{$env.API_KEY}}
```
**Result**: `https://api.example.com/data?key=secret123`
---
## Template from Real Workflow
**Based on n8n template #2947** (Weather to Slack)
### Workflow Structure
Webhook → OpenStreetMap API → Weather API → Slack
### Webhook Slash Command
**Input**: `/weather London`
**Webhook receives**:
```json
{
"body": {
"text": "London"
}
}
```
### OpenStreetMap API
**URL**:
```
https://nominatim.openstreetmap.org/search?q={{$json.body.text}}&format=json
```
### Weather API (NWS)
**URL**:
```
https://api.weather.gov/points/{{$node["OpenStreetMap"].json[0].lat}},{{$node["OpenStreetMap"].json[0].lon}}
```
### Slack Message
```
Weather for {{$json.body.text}}:
Temperature: {{$node["Weather API"].json.properties.temperature.value}}°C
Conditions: {{$node["Weather API"].json.properties.shortForecast}}
```
---
## Summary
**Key Patterns**:
1. Webhook data is under `.body`
2. Use `{{}}` for expressions (except Code nodes)
3. Reference other nodes with `$node["Node Name"].json`
4. Use brackets for field names with spaces
5. Node names are case-sensitive
**Most Common Uses**:
- `{{$json.body.field}}` - Webhook data
- `{{$node["Name"].json.field}}` - Other node data
- `{{$now.toFormat('yyyy-MM-dd')}}` - Timestamps
- `{{$json.array[0].field}}` - Array access
- `{{$json.field || 'default'}}` - Default values
---
**Related**: See [COMMON_MISTAKES.md](COMMON_MISTAKES.md) for error examples and fixes.

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# n8n Expression Syntax
Expert guide for writing correct n8n expressions in workflows.
---
## Purpose
Teaches correct n8n expression syntax ({{ }} patterns) and fixes common mistakes, especially the critical webhook data structure gotcha.
## Activates On
- expression
- {{}} syntax
- $json, $node, $now, $env
- webhook data
- troubleshoot expression error
- undefined in workflow
## File Count
4 files, ~450 lines total
## Dependencies
**n8n-mcp tools**:
- None directly (syntax knowledge skill)
- Works with n8n-mcp validation tools
**Related skills**:
- n8n Workflow Patterns (uses expressions in examples)
- n8n MCP Tools Expert (validates expressions)
- n8n Node Configuration (when expressions are needed)
## Coverage
### Core Topics
- Expression format ({{ }})
- Core variables ($json, $node, $now, $env)
- **Webhook data structure** ($json.body.*)
- When NOT to use expressions (Code nodes)
### Common Patterns
- Accessing nested fields
- Referencing other nodes
- Array and object access
- Date/time formatting
- String manipulation
### Error Prevention
- 15 common mistakes with fixes
- Quick reference table
- Debugging process
## Evaluations
4 scenarios (100% coverage expected):
1. **eval-001**: Missing curly braces
2. **eval-002**: Webhook body data access (critical!)
3. **eval-003**: Code node vs expression confusion
4. **eval-004**: Node reference syntax
## Key Features
✅ **Critical Gotcha Highlighted**: Webhook data under `.body`
✅ **Real Examples**: From MCP testing and real templates
✅ **Quick Fixes Table**: Fast reference for common errors
✅ **Code vs Expression**: Clear distinction
✅ **Comprehensive**: Covers 95% of expression use cases
## Files
- **SKILL.md** (285 lines) - Main content with all essential knowledge
- **COMMON_MISTAKES.md** (380 lines) - Complete error catalog with 15 common mistakes
- **EXAMPLES.md** (450 lines) - 10 real working examples
- **README.md** (this file) - Skill metadata
## Success Metrics
**Expected outcomes**:
- Users correctly wrap expressions in {{ }}
- Zero webhook `.body` access errors
- No expressions used in Code nodes
- Correct $node reference syntax
## Last Updated
2025-10-20
---
**Part of**: n8n-skills repository
**Conceived by**: Romuald Członkowski - [www.aiadvisors.pl/en](https://www.aiadvisors.pl/en)

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---
name: n8n-expression-syntax
description: Validate n8n expression syntax and fix common errors. Use when writing n8n expressions, using {{}} syntax, accessing $json/$node variables, troubleshooting expression errors, or working with webhook data in workflows.
---
# n8n Expression Syntax
Expert guide for writing correct n8n expressions in workflows.
---
## Expression Format
All dynamic content in n8n uses **double curly braces**:
```
{{expression}}
```
**Examples**:
```
✅ {{$json.email}}
✅ {{$json.body.name}}
✅ {{$node["HTTP Request"].json.data}}
❌ $json.email (no braces - treated as literal text)
❌ {$json.email} (single braces - invalid)
```
---
## Core Variables
### $json - Current Node Output
Access data from the current node:
```javascript
{{$json.fieldName}}
{{$json['field with spaces']}}
{{$json.nested.property}}
{{$json.items[0].name}}
```
### $node - Reference Other Nodes
Access data from any previous node:
```javascript
{{$node["Node Name"].json.fieldName}}
{{$node["HTTP Request"].json.data}}
{{$node["Webhook"].json.body.email}}
```
**Important**:
- Node names **must** be in quotes
- Node names are **case-sensitive**
- Must match exact node name from workflow
### $now - Current Timestamp
Access current date/time:
```javascript
{{$now}}
{{$now.toFormat('yyyy-MM-dd')}}
{{$now.toFormat('HH:mm:ss')}}
{{$now.plus({days: 7})}}
```
### $env - Environment Variables
Access environment variables:
```javascript
{{$env.API_KEY}}
{{$env.DATABASE_URL}}
```
---
## 🚨 CRITICAL: Webhook Data Structure
**Most Common Mistake**: Webhook data is **NOT** at the root!
### Webhook Node Output Structure
```javascript
{
"headers": {...},
"params": {...},
"query": {...},
"body": { // ⚠️ USER DATA IS HERE!
"name": "John",
"email": "john@example.com",
"message": "Hello"
}
}
```
### Correct Webhook Data Access
```javascript
❌ WRONG: {{$json.name}}
❌ WRONG: {{$json.email}}
✅ CORRECT: {{$json.body.name}}
✅ CORRECT: {{$json.body.email}}
✅ CORRECT: {{$json.body.message}}
```
**Why**: Webhook node wraps incoming data under `.body` property to preserve headers, params, and query parameters.
---
## Common Patterns
### Access Nested Fields
```javascript
// Simple nesting
{{$json.user.email}}
// Array access
{{$json.data[0].name}}
{{$json.items[0].id}}
// Bracket notation for spaces
{{$json['field name']}}
{{$json['user data']['first name']}}
```
### Reference Other Nodes
```javascript
// Node without spaces
{{$node["Set"].json.value}}
// Node with spaces (common!)
{{$node["HTTP Request"].json.data}}
{{$node["Respond to Webhook"].json.message}}
// Webhook node
{{$node["Webhook"].json.body.email}}
```
### Combine Variables
```javascript
// Concatenation (automatic)
Hello {{$json.body.name}}!
// In URLs
https://api.example.com/users/{{$json.body.user_id}}
// In object properties
{
"name": "={{$json.body.name}}",
"email": "={{$json.body.email}}"
}
```
---
## When NOT to Use Expressions
### ❌ Code Nodes
Code nodes use **direct JavaScript access**, NOT expressions!
```javascript
// ❌ WRONG in Code node
const email = '={{$json.email}}';
const name = '{{$json.body.name}}';
// ✅ CORRECT in Code node
const email = $json.email;
const name = $json.body.name;
// Or using Code node API
const email = $input.item.json.email;
const allItems = $input.all();
```
### ❌ Webhook Paths
```javascript
// ❌ WRONG
path: "{{$json.user_id}}/webhook"
// ✅ CORRECT
path: "user-webhook" // Static paths only
```
### ❌ Credential Fields
```javascript
// ❌ WRONG
apiKey: "={{$env.API_KEY}}"
// ✅ CORRECT
Use n8n credential system, not expressions
```
---
## Validation Rules
### 1. Always Use {{}}
Expressions **must** be wrapped in double curly braces.
```javascript
❌ $json.field
✅ {{$json.field}}
```
### 2. Use Quotes for Spaces
Field or node names with spaces require **bracket notation**:
```javascript
❌ {{$json.field name}}
✅ {{$json['field name']}}
❌ {{$node.HTTP Request.json}}
✅ {{$node["HTTP Request"].json}}
```
### 3. Match Exact Node Names
Node references are **case-sensitive**:
```javascript
❌ {{$node["http request"].json}} // lowercase
❌ {{$node["Http Request"].json}} // wrong case
✅ {{$node["HTTP Request"].json}} // exact match
```
### 4. No Nested {{}}
Don't double-wrap expressions:
```javascript
❌ {{{$json.field}}}
✅ {{$json.field}}
```
---
## Common Mistakes
For complete error catalog with fixes, see [COMMON_MISTAKES.md](COMMON_MISTAKES.md)
### Quick Fixes
| Mistake | Fix |
|---------|-----|
| `$json.field` | `{{$json.field}}` |
| `{{$json.field name}}` | `{{$json['field name']}}` |
| `{{$node.HTTP Request}}` | `{{$node["HTTP Request"]}}` |
| `{{{$json.field}}}` | `{{$json.field}}` |
| `{{$json.name}}` (webhook) | `{{$json.body.name}}` |
| `'={{$json.email}}'` (Code node) | `$json.email` |
---
## Working Examples
For real workflow examples, see [EXAMPLES.md](EXAMPLES.md)
### Example 1: Webhook to Slack
**Webhook receives**:
```json
{
"body": {
"name": "John Doe",
"email": "john@example.com",
"message": "Hello!"
}
}
```
**In Slack node text field**:
```
New form submission!
Name: {{$json.body.name}}
Email: {{$json.body.email}}
Message: {{$json.body.message}}
```
### Example 2: HTTP Request to Email
**HTTP Request returns**:
```json
{
"data": {
"items": [
{"name": "Product 1", "price": 29.99}
]
}
}
```
**In Email node** (reference HTTP Request):
```
Product: {{$node["HTTP Request"].json.data.items[0].name}}
Price: ${{$node["HTTP Request"].json.data.items[0].price}}
```
### Example 3: Format Timestamp
```javascript
// Current date
{{$now.toFormat('yyyy-MM-dd')}}
// Result: 2025-10-20
// Time
{{$now.toFormat('HH:mm:ss')}}
// Result: 14:30:45
// Full datetime
{{$now.toFormat('yyyy-MM-dd HH:mm')}}
// Result: 2025-10-20 14:30
```
---
## Data Type Handling
### Arrays
```javascript
// First item
{{$json.users[0].email}}
// Array length
{{$json.users.length}}
// Last item
{{$json.users[$json.users.length - 1].name}}
```
### Objects
```javascript
// Dot notation (no spaces)
{{$json.user.email}}
// Bracket notation (with spaces or dynamic)
{{$json['user data'].email}}
```
### Strings
```javascript
// Concatenation (automatic)
Hello {{$json.name}}!
// String methods
{{$json.email.toLowerCase()}}
{{$json.name.toUpperCase()}}
```
### Numbers
```javascript
// Direct use
{{$json.price}}
// Math operations
{{$json.price * 1.1}} // Add 10%
{{$json.quantity + 5}}
```
---
## Advanced Patterns
### Conditional Content
```javascript
// Ternary operator
{{$json.status === 'active' ? 'Active User' : 'Inactive User'}}
// Default values
{{$json.email || 'no-email@example.com'}}
```
### Date Manipulation
```javascript
// Add days
{{$now.plus({days: 7}).toFormat('yyyy-MM-dd')}}
// Subtract hours
{{$now.minus({hours: 24}).toISO()}}
// Set specific date
{{DateTime.fromISO('2025-12-25').toFormat('MMMM dd, yyyy')}}
```
### String Manipulation
```javascript
// Substring
{{$json.email.substring(0, 5)}}
// Replace
{{$json.message.replace('old', 'new')}}
// Split and join
{{$json.tags.split(',').join(', ')}}
```
---
## Debugging Expressions
### Test in Expression Editor
1. Click field with expression
2. Open expression editor (click "fx" icon)
3. See live preview of result
4. Check for errors highlighted in red
### Common Error Messages
**"Cannot read property 'X' of undefined"**
→ Parent object doesn't exist
→ Check your data path
**"X is not a function"**
→ Trying to call method on non-function
→ Check variable type
**Expression shows as literal text**
→ Missing {{ }}
→ Add curly braces
---
## Expression Helpers
### Available Methods
**String**:
- `.toLowerCase()`, `.toUpperCase()`
- `.trim()`, `.replace()`, `.substring()`
- `.split()`, `.includes()`
**Array**:
- `.length`, `.map()`, `.filter()`
- `.find()`, `.join()`, `.slice()`
**DateTime** (Luxon):
- `.toFormat()`, `.toISO()`, `.toLocal()`
- `.plus()`, `.minus()`, `.set()`
**Number**:
- `.toFixed()`, `.toString()`
- Math operations: `+`, `-`, `*`, `/`, `%`
---
## Best Practices
### ✅ Do
- Always use {{ }} for dynamic content
- Use bracket notation for field names with spaces
- Reference webhook data from `.body`
- Use $node for data from other nodes
- Test expressions in expression editor
### ❌ Don't
- Don't use expressions in Code nodes
- Don't forget quotes around node names with spaces
- Don't double-wrap with extra {{ }}
- Don't assume webhook data is at root (it's under .body!)
- Don't use expressions in webhook paths or credentials
---
## Related Skills
- **n8n MCP Tools Expert**: Learn how to validate expressions using MCP tools
- **n8n Workflow Patterns**: See expressions in real workflow examples
- **n8n Node Configuration**: Understand when expressions are needed
---
## Summary
**Essential Rules**:
1. Wrap expressions in {{ }}
2. Webhook data is under `.body`
3. No {{ }} in Code nodes
4. Quote node names with spaces
5. Node names are case-sensitive
**Most Common Mistakes**:
- Missing {{ }} → Add braces
- `{{$json.name}}` in webhooks → Use `{{$json.body.name}}`
- `{{$json.email}}` in Code → Use `$json.email`
- `{{$node.HTTP Request}}` → Use `{{$node["HTTP Request"]}}`
For more details, see:
- [COMMON_MISTAKES.md](COMMON_MISTAKES.md) - Complete error catalog
- [EXAMPLES.md](EXAMPLES.md) - Real workflow examples
---
**Need Help?** Reference the n8n expression documentation or use n8n-mcp validation tools to check your expressions.

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# Built-in Functions - JavaScript Code Node
Complete reference for n8n's built-in JavaScript functions and helpers.
---
## Overview
n8n Code nodes provide powerful built-in functions beyond standard JavaScript. This guide covers:
1. **$helpers.httpRequest()** - Make HTTP requests
2. **DateTime (Luxon)** - Advanced date/time operations
3. **$jmespath()** - Query JSON structures
4. **$getWorkflowStaticData()** - Persistent storage
5. **Standard JavaScript Globals** - Math, JSON, console, etc.
6. **Available Node.js Modules** - crypto, Buffer, URL
---
## 1. $helpers.httpRequest() - HTTP Requests
Make HTTP requests directly from Code nodes without using HTTP Request node.
### Basic Usage
```javascript
const response = await $helpers.httpRequest({
method: 'GET',
url: 'https://api.example.com/users'
});
return [{json: {data: response}}];
```
### Complete Options
```javascript
const response = await $helpers.httpRequest({
method: 'POST', // GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS
url: 'https://api.example.com/users',
headers: {
'Authorization': 'Bearer token123',
'Content-Type': 'application/json',
'User-Agent': 'n8n-workflow'
},
body: {
name: 'John Doe',
email: 'john@example.com'
},
qs: { // Query string parameters
page: 1,
limit: 10
},
timeout: 10000, // Milliseconds (default: no timeout)
json: true, // Auto-parse JSON response (default: true)
simple: false, // Don't throw on HTTP errors (default: true)
resolveWithFullResponse: false // Return only body (default: false)
});
```
### GET Request
```javascript
// Simple GET
const users = await $helpers.httpRequest({
method: 'GET',
url: 'https://api.example.com/users'
});
return [{json: {users}}];
```
```javascript
// GET with query parameters
const results = await $helpers.httpRequest({
method: 'GET',
url: 'https://api.example.com/search',
qs: {
q: 'javascript',
page: 1,
per_page: 50
}
});
return [{json: results}];
```
### POST Request
```javascript
// POST with JSON body
const newUser = await $helpers.httpRequest({
method: 'POST',
url: 'https://api.example.com/users',
headers: {
'Content-Type': 'application/json',
'Authorization': 'Bearer ' + $env.API_KEY
},
body: {
name: $json.body.name,
email: $json.body.email,
role: 'user'
}
});
return [{json: newUser}];
```
### PUT/PATCH Request
```javascript
// Update resource
const updated = await $helpers.httpRequest({
method: 'PATCH',
url: `https://api.example.com/users/${userId}`,
body: {
name: 'Updated Name',
status: 'active'
}
});
return [{json: updated}];
```
### DELETE Request
```javascript
// Delete resource
await $helpers.httpRequest({
method: 'DELETE',
url: `https://api.example.com/users/${userId}`,
headers: {
'Authorization': 'Bearer ' + $env.API_KEY
}
});
return [{json: {deleted: true, userId}}];
```
### Authentication Patterns
```javascript
// Bearer Token
const response = await $helpers.httpRequest({
url: 'https://api.example.com/data',
headers: {
'Authorization': `Bearer ${$env.API_TOKEN}`
}
});
```
```javascript
// API Key in Header
const response = await $helpers.httpRequest({
url: 'https://api.example.com/data',
headers: {
'X-API-Key': $env.API_KEY
}
});
```
```javascript
// Basic Auth (manual)
const credentials = Buffer.from(`${username}:${password}`).toString('base64');
const response = await $helpers.httpRequest({
url: 'https://api.example.com/data',
headers: {
'Authorization': `Basic ${credentials}`
}
});
```
### Error Handling
```javascript
// Handle HTTP errors gracefully
try {
const response = await $helpers.httpRequest({
method: 'GET',
url: 'https://api.example.com/users',
simple: false // Don't throw on 4xx/5xx
});
if (response.statusCode >= 200 && response.statusCode < 300) {
return [{json: {success: true, data: response.body}}];
} else {
return [{
json: {
success: false,
status: response.statusCode,
error: response.body
}
}];
}
} catch (error) {
return [{
json: {
success: false,
error: error.message
}
}];
}
```
### Full Response Access
```javascript
// Get full response including headers and status
const response = await $helpers.httpRequest({
url: 'https://api.example.com/data',
resolveWithFullResponse: true
});
return [{
json: {
statusCode: response.statusCode,
headers: response.headers,
body: response.body,
rateLimit: response.headers['x-ratelimit-remaining']
}
}];
```
---
## 2. DateTime (Luxon) - Date & Time Operations
n8n includes Luxon for powerful date/time handling. Access via `DateTime` global.
### Current Date/Time
```javascript
// Current time
const now = DateTime.now();
// Current time in specific timezone
const nowTokyo = DateTime.now().setZone('Asia/Tokyo');
// Today at midnight
const today = DateTime.now().startOf('day');
return [{
json: {
iso: now.toISO(), // "2025-01-20T15:30:00.000Z"
formatted: now.toFormat('yyyy-MM-dd HH:mm:ss'), // "2025-01-20 15:30:00"
unix: now.toSeconds(), // Unix timestamp
millis: now.toMillis() // Milliseconds since epoch
}
}];
```
### Formatting Dates
```javascript
const now = DateTime.now();
return [{
json: {
isoFormat: now.toISO(), // ISO 8601: "2025-01-20T15:30:00.000Z"
sqlFormat: now.toSQL(), // SQL: "2025-01-20 15:30:00.000"
httpFormat: now.toHTTP(), // HTTP: "Mon, 20 Jan 2025 15:30:00 GMT"
// Custom formats
dateOnly: now.toFormat('yyyy-MM-dd'), // "2025-01-20"
timeOnly: now.toFormat('HH:mm:ss'), // "15:30:00"
readable: now.toFormat('MMMM dd, yyyy'), // "January 20, 2025"
compact: now.toFormat('yyyyMMdd'), // "20250120"
withDay: now.toFormat('EEEE, MMMM dd, yyyy'), // "Monday, January 20, 2025"
custom: now.toFormat('dd/MM/yy HH:mm') // "20/01/25 15:30"
}
}];
```
### Parsing Dates
```javascript
// From ISO string
const dt1 = DateTime.fromISO('2025-01-20T15:30:00');
// From specific format
const dt2 = DateTime.fromFormat('01/20/2025', 'MM/dd/yyyy');
// From SQL
const dt3 = DateTime.fromSQL('2025-01-20 15:30:00');
// From Unix timestamp
const dt4 = DateTime.fromSeconds(1737384600);
// From milliseconds
const dt5 = DateTime.fromMillis(1737384600000);
return [{json: {parsed: dt1.toISO()}}];
```
### Date Arithmetic
```javascript
const now = DateTime.now();
return [{
json: {
// Adding time
tomorrow: now.plus({days: 1}).toISO(),
nextWeek: now.plus({weeks: 1}).toISO(),
nextMonth: now.plus({months: 1}).toISO(),
inTwoHours: now.plus({hours: 2}).toISO(),
// Subtracting time
yesterday: now.minus({days: 1}).toISO(),
lastWeek: now.minus({weeks: 1}).toISO(),
lastMonth: now.minus({months: 1}).toISO(),
twoHoursAgo: now.minus({hours: 2}).toISO(),
// Complex operations
in90Days: now.plus({days: 90}).toFormat('yyyy-MM-dd'),
in6Months: now.plus({months: 6}).toFormat('yyyy-MM-dd')
}
}];
```
### Time Comparisons
```javascript
const now = DateTime.now();
const targetDate = DateTime.fromISO('2025-12-31');
return [{
json: {
// Comparisons
isFuture: targetDate > now,
isPast: targetDate < now,
isEqual: targetDate.equals(now),
// Differences
daysUntil: targetDate.diff(now, 'days').days,
hoursUntil: targetDate.diff(now, 'hours').hours,
monthsUntil: targetDate.diff(now, 'months').months,
// Detailed difference
detailedDiff: targetDate.diff(now, ['months', 'days', 'hours']).toObject()
}
}];
```
### Timezone Operations
```javascript
const now = DateTime.now();
return [{
json: {
// Current timezone
local: now.toISO(),
// Convert to different timezone
tokyo: now.setZone('Asia/Tokyo').toISO(),
newYork: now.setZone('America/New_York').toISO(),
london: now.setZone('Europe/London').toISO(),
utc: now.toUTC().toISO(),
// Get timezone info
timezone: now.zoneName, // "America/Los_Angeles"
offset: now.offset, // Offset in minutes
offsetFormatted: now.toFormat('ZZ') // "+08:00"
}
}];
```
### Start/End of Period
```javascript
const now = DateTime.now();
return [{
json: {
startOfDay: now.startOf('day').toISO(),
endOfDay: now.endOf('day').toISO(),
startOfWeek: now.startOf('week').toISO(),
endOfWeek: now.endOf('week').toISO(),
startOfMonth: now.startOf('month').toISO(),
endOfMonth: now.endOf('month').toISO(),
startOfYear: now.startOf('year').toISO(),
endOfYear: now.endOf('year').toISO()
}
}];
```
### Weekday & Month Info
```javascript
const now = DateTime.now();
return [{
json: {
// Day info
weekday: now.weekday, // 1 = Monday, 7 = Sunday
weekdayShort: now.weekdayShort, // "Mon"
weekdayLong: now.weekdayLong, // "Monday"
isWeekend: now.weekday > 5, // Saturday or Sunday
// Month info
month: now.month, // 1-12
monthShort: now.monthShort, // "Jan"
monthLong: now.monthLong, // "January"
// Year info
year: now.year, // 2025
quarter: now.quarter, // 1-4
daysInMonth: now.daysInMonth // 28-31
}
}];
```
---
## 3. $jmespath() - JSON Querying
Query and transform JSON structures using JMESPath syntax.
### Basic Queries
```javascript
const data = $input.first().json;
// Extract specific field
const names = $jmespath(data, 'users[*].name');
// Filter array
const adults = $jmespath(data, 'users[?age >= `18`]');
// Get specific index
const firstUser = $jmespath(data, 'users[0]');
return [{json: {names, adults, firstUser}}];
```
### Advanced Queries
```javascript
const data = $input.first().json;
// Sort and slice
const top5 = $jmespath(data, 'users | sort_by(@, &score) | reverse(@) | [0:5]');
// Extract nested fields
const emails = $jmespath(data, 'users[*].contact.email');
// Multi-field extraction
const simplified = $jmespath(data, 'users[*].{name: name, email: contact.email}');
// Conditional filtering
const premium = $jmespath(data, 'users[?subscription.tier == `premium`]');
return [{json: {top5, emails, simplified, premium}}];
```
### Common Patterns
```javascript
// Pattern 1: Filter and project
const query1 = $jmespath(data, 'products[?price > `100`].{name: name, price: price}');
// Pattern 2: Aggregate functions
const query2 = $jmespath(data, 'sum(products[*].price)');
const query3 = $jmespath(data, 'max(products[*].price)');
const query4 = $jmespath(data, 'length(products)');
// Pattern 3: Nested filtering
const query5 = $jmespath(data, 'categories[*].products[?inStock == `true`]');
return [{json: {query1, query2, query3, query4, query5}}];
```
---
## 4. $getWorkflowStaticData() - Persistent Storage
Store data that persists across workflow executions.
### Basic Usage
```javascript
// Get static data storage
const staticData = $getWorkflowStaticData();
// Initialize counter if doesn't exist
if (!staticData.counter) {
staticData.counter = 0;
}
// Increment counter
staticData.counter++;
return [{
json: {
executionCount: staticData.counter
}
}];
```
### Use Cases
```javascript
// Use Case 1: Rate limiting
const staticData = $getWorkflowStaticData();
const now = Date.now();
if (!staticData.lastRun) {
staticData.lastRun = now;
staticData.runCount = 1;
} else {
const timeSinceLastRun = now - staticData.lastRun;
if (timeSinceLastRun < 60000) { // Less than 1 minute
return [{json: {error: 'Rate limit: wait 1 minute between runs'}}];
}
staticData.lastRun = now;
staticData.runCount++;
}
return [{json: {allowed: true, totalRuns: staticData.runCount}}];
```
```javascript
// Use Case 2: Tracking last processed ID
const staticData = $getWorkflowStaticData();
const currentItems = $input.all();
// Get last processed ID
const lastId = staticData.lastProcessedId || 0;
// Filter only new items
const newItems = currentItems.filter(item => item.json.id > lastId);
// Update last processed ID
if (newItems.length > 0) {
staticData.lastProcessedId = Math.max(...newItems.map(item => item.json.id));
}
return newItems;
```
```javascript
// Use Case 3: Accumulating results
const staticData = $getWorkflowStaticData();
if (!staticData.accumulated) {
staticData.accumulated = [];
}
// Add current items to accumulated list
const currentData = $input.all().map(item => item.json);
staticData.accumulated.push(...currentData);
return [{
json: {
currentBatch: currentData.length,
totalAccumulated: staticData.accumulated.length,
allData: staticData.accumulated
}
}];
```
---
## 5. Standard JavaScript Globals
### Math Object
```javascript
return [{
json: {
// Rounding
rounded: Math.round(3.7), // 4
floor: Math.floor(3.7), // 3
ceil: Math.ceil(3.2), // 4
// Min/Max
max: Math.max(1, 5, 3, 9, 2), // 9
min: Math.min(1, 5, 3, 9, 2), // 1
// Random
random: Math.random(), // 0-1
randomInt: Math.floor(Math.random() * 100), // 0-99
// Other
abs: Math.abs(-5), // 5
sqrt: Math.sqrt(16), // 4
pow: Math.pow(2, 3) // 8
}
}];
```
### JSON Object
```javascript
// Parse JSON string
const jsonString = '{"name": "John", "age": 30}';
const parsed = JSON.parse(jsonString);
// Stringify object
const obj = {name: "John", age: 30};
const stringified = JSON.stringify(obj);
// Pretty print
const pretty = JSON.stringify(obj, null, 2);
return [{json: {parsed, stringified, pretty}}];
```
### console Object
```javascript
// Debug logging (appears in browser console, press F12)
console.log('Processing items:', $input.all().length);
console.log('First item:', $input.first().json);
// Other console methods
console.error('Error message');
console.warn('Warning message');
console.info('Info message');
// Continues to return data
return [{json: {processed: true}}];
```
### Object Methods
```javascript
const obj = {name: "John", age: 30, city: "NYC"};
return [{
json: {
keys: Object.keys(obj), // ["name", "age", "city"]
values: Object.values(obj), // ["John", 30, "NYC"]
entries: Object.entries(obj), // [["name", "John"], ...]
// Check property
hasName: 'name' in obj, // true
// Merge objects
merged: Object.assign({}, obj, {country: "USA"})
}
}];
```
### Array Methods
```javascript
const arr = [1, 2, 3, 4, 5];
return [{
json: {
mapped: arr.map(x => x * 2), // [2, 4, 6, 8, 10]
filtered: arr.filter(x => x > 2), // [3, 4, 5]
reduced: arr.reduce((sum, x) => sum + x, 0), // 15
some: arr.some(x => x > 3), // true
every: arr.every(x => x > 0), // true
find: arr.find(x => x > 3), // 4
includes: arr.includes(3), // true
joined: arr.join(', ') // "1, 2, 3, 4, 5"
}
}];
```
---
## 6. Available Node.js Modules
### crypto Module
```javascript
const crypto = require('crypto');
// Hash functions
const hash = crypto.createHash('sha256')
.update('my secret text')
.digest('hex');
// MD5 hash
const md5 = crypto.createHash('md5')
.update('my text')
.digest('hex');
// Random values
const randomBytes = crypto.randomBytes(16).toString('hex');
return [{json: {hash, md5, randomBytes}}];
```
### Buffer (built-in)
```javascript
// Base64 encoding
const encoded = Buffer.from('Hello World').toString('base64');
// Base64 decoding
const decoded = Buffer.from(encoded, 'base64').toString();
// Hex encoding
const hex = Buffer.from('Hello').toString('hex');
return [{json: {encoded, decoded, hex}}];
```
### URL / URLSearchParams
```javascript
// Parse URL
const url = new URL('https://example.com/path?param1=value1&param2=value2');
// Build query string
const params = new URLSearchParams({
search: 'query',
page: 1,
limit: 10
});
return [{
json: {
host: url.host,
pathname: url.pathname,
search: url.search,
queryString: params.toString() // "search=query&page=1&limit=10"
}
}];
```
---
## What's NOT Available
**External npm packages are NOT available:**
- ❌ axios
- ❌ lodash
- ❌ moment (use DateTime/Luxon instead)
- ❌ request
- ❌ Any other npm package
**Workaround**: Use $helpers.httpRequest() for HTTP, or add data to workflow via HTTP Request node.
---
## Summary
**Most Useful Built-ins**:
1. **$helpers.httpRequest()** - API calls without HTTP Request node
2. **DateTime** - Professional date/time handling
3. **$jmespath()** - Complex JSON queries
4. **Math, JSON, Object, Array** - Standard JavaScript utilities
**Common Patterns**:
- API calls: Use $helpers.httpRequest()
- Date operations: Use DateTime (Luxon)
- Data filtering: Use $jmespath() or JavaScript .filter()
- Persistent data: Use $getWorkflowStaticData()
- Hashing: Use crypto module
**See Also**:
- [SKILL.md](SKILL.md) - Overview
- [COMMON_PATTERNS.md](COMMON_PATTERNS.md) - Real usage examples
- [ERROR_PATTERNS.md](ERROR_PATTERNS.md) - Error prevention

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# Data Access Patterns - JavaScript Code Node
Comprehensive guide to accessing data in n8n Code nodes using JavaScript.
---
## Overview
In n8n Code nodes, you access data from previous nodes using built-in variables and methods. Understanding which method to use is critical for correct workflow execution.
**Data Access Priority** (by common usage):
1. **`$input.all()`** - Most common - Batch operations, aggregations
2. **`$input.first()`** - Very common - Single item operations
3. **`$input.item`** - Common - Each Item mode only
4. **`$node["NodeName"].json`** - Specific node references
5. **`$json`** - Direct current item (legacy, use `$input` instead)
---
## Pattern 1: $input.all() - Process All Items
**Usage**: Most common pattern for batch processing
**When to use:**
- Processing multiple records
- Aggregating data (sum, count, average)
- Filtering arrays
- Transforming datasets
- Comparing items
- Sorting or ranking
### Basic Usage
```javascript
// Get all items from previous node
const allItems = $input.all();
// allItems is an array of objects like:
// [
// {json: {id: 1, name: "Alice"}},
// {json: {id: 2, name: "Bob"}}
// ]
console.log(`Received ${allItems.length} items`);
return allItems;
```
### Example 1: Filter Active Items
```javascript
const allItems = $input.all();
// Filter only active items
const activeItems = allItems.filter(item => item.json.status === 'active');
return activeItems;
```
### Example 2: Transform All Items
```javascript
const allItems = $input.all();
// Map to new structure
const transformed = allItems.map(item => ({
json: {
id: item.json.id,
fullName: `${item.json.firstName} ${item.json.lastName}`,
email: item.json.email,
processedAt: new Date().toISOString()
}
}));
return transformed;
```
### Example 3: Aggregate Data
```javascript
const allItems = $input.all();
// Calculate total
const total = allItems.reduce((sum, item) => {
return sum + (item.json.amount || 0);
}, 0);
return [{
json: {
total,
count: allItems.length,
average: total / allItems.length
}
}];
```
### Example 4: Sort and Limit
```javascript
const allItems = $input.all();
// Get top 5 by score
const topFive = allItems
.sort((a, b) => (b.json.score || 0) - (a.json.score || 0))
.slice(0, 5);
return topFive.map(item => ({json: item.json}));
```
### Example 5: Group By Category
```javascript
const allItems = $input.all();
// Group items by category
const grouped = {};
for (const item of allItems) {
const category = item.json.category || 'Uncategorized';
if (!grouped[category]) {
grouped[category] = [];
}
grouped[category].push(item.json);
}
// Convert to array format
return Object.entries(grouped).map(([category, items]) => ({
json: {
category,
items,
count: items.length
}
}));
```
### Example 6: Deduplicate by ID
```javascript
const allItems = $input.all();
// Remove duplicates by ID
const seen = new Set();
const unique = [];
for (const item of allItems) {
const id = item.json.id;
if (!seen.has(id)) {
seen.add(id);
unique.push(item);
}
}
return unique;
```
---
## Pattern 2: $input.first() - Get First Item
**Usage**: Very common for single-item operations
**When to use:**
- Previous node returns single object
- Working with API responses
- Getting initial/first data point
- Configuration or metadata access
### Basic Usage
```javascript
// Get first item from previous node
const firstItem = $input.first();
// Access the JSON data
const data = firstItem.json;
console.log('First item:', data);
return [{json: data}];
```
### Example 1: Process Single API Response
```javascript
// Get API response (typically single object)
const response = $input.first().json;
// Extract what you need
return [{
json: {
userId: response.data.user.id,
userName: response.data.user.name,
status: response.status,
fetchedAt: new Date().toISOString()
}
}];
```
### Example 2: Transform Single Object
```javascript
const data = $input.first().json;
// Transform structure
return [{
json: {
id: data.id,
contact: {
email: data.email,
phone: data.phone
},
address: {
street: data.street,
city: data.city,
zip: data.zip
}
}
}];
```
### Example 3: Validate Single Item
```javascript
const item = $input.first().json;
// Validation logic
const isValid = item.email && item.email.includes('@');
return [{
json: {
...item,
valid: isValid,
validatedAt: new Date().toISOString()
}
}];
```
### Example 4: Extract Nested Data
```javascript
const response = $input.first().json;
// Navigate nested structure
const users = response.data?.users || [];
return users.map(user => ({
json: {
id: user.id,
name: user.profile?.name || 'Unknown',
email: user.contact?.email || 'no-email'
}
}));
```
### Example 5: Combine with Other Methods
```javascript
// Get first item's data
const firstData = $input.first().json;
// Use it to filter all items
const allItems = $input.all();
const matching = allItems.filter(item =>
item.json.category === firstData.targetCategory
);
return matching;
```
---
## Pattern 3: $input.item - Current Item (Each Item Mode)
**Usage**: Common in "Run Once for Each Item" mode
**When to use:**
- Mode is set to "Run Once for Each Item"
- Need to process items independently
- Per-item API calls or validations
- Item-specific error handling
**IMPORTANT**: Only use in "Each Item" mode. Will be undefined in "All Items" mode.
### Basic Usage
```javascript
// In "Run Once for Each Item" mode
const currentItem = $input.item;
const data = currentItem.json;
console.log('Processing item:', data.id);
return [{
json: {
...data,
processed: true
}
}];
```
### Example 1: Add Processing Metadata
```javascript
const item = $input.item;
return [{
json: {
...item.json,
processed: true,
processedAt: new Date().toISOString(),
processingDuration: Math.random() * 1000 // Simulated duration
}
}];
```
### Example 2: Per-Item Validation
```javascript
const item = $input.item;
const data = item.json;
// Validate this specific item
const errors = [];
if (!data.email) errors.push('Email required');
if (!data.name) errors.push('Name required');
if (data.age && data.age < 18) errors.push('Must be 18+');
return [{
json: {
...data,
valid: errors.length === 0,
errors: errors.length > 0 ? errors : undefined
}
}];
```
### Example 3: Item-Specific API Call
```javascript
const item = $input.item;
const userId = item.json.userId;
// Make API call specific to this item
const response = await $helpers.httpRequest({
method: 'GET',
url: `https://api.example.com/users/${userId}/details`
});
return [{
json: {
...item.json,
details: response
}
}];
```
### Example 4: Conditional Processing
```javascript
const item = $input.item;
const data = item.json;
// Process based on item type
if (data.type === 'premium') {
return [{
json: {
...data,
discount: 0.20,
tier: 'premium'
}
}];
} else {
return [{
json: {
...data,
discount: 0.05,
tier: 'standard'
}
}];
}
```
---
## Pattern 4: $node - Reference Other Nodes
**Usage**: Less common, but powerful for specific scenarios
**When to use:**
- Need data from specific named node
- Combining data from multiple nodes
- Accessing metadata about workflow execution
### Basic Usage
```javascript
// Get output from specific node
const webhookData = $node["Webhook"].json;
const apiData = $node["HTTP Request"].json;
return [{
json: {
fromWebhook: webhookData,
fromAPI: apiData
}
}];
```
### Example 1: Combine Multiple Sources
```javascript
// Reference multiple nodes
const webhook = $node["Webhook"].json;
const database = $node["Postgres"].json;
const api = $node["HTTP Request"].json;
return [{
json: {
combined: {
webhook: webhook.body,
dbRecords: database.length,
apiResponse: api.status
},
processedAt: new Date().toISOString()
}
}];
```
### Example 2: Compare Across Nodes
```javascript
const oldData = $node["Get Old Data"].json;
const newData = $node["Get New Data"].json;
// Compare
const changes = {
added: newData.filter(n => !oldData.find(o => o.id === n.id)),
removed: oldData.filter(o => !newData.find(n => n.id === o.id)),
modified: newData.filter(n => {
const old = oldData.find(o => o.id === n.id);
return old && JSON.stringify(old) !== JSON.stringify(n);
})
};
return [{
json: {
changes,
summary: {
added: changes.added.length,
removed: changes.removed.length,
modified: changes.modified.length
}
}
}];
```
### Example 3: Access Node Metadata
```javascript
// Get data from specific execution path
const ifTrueBranch = $node["IF True"].json;
const ifFalseBranch = $node["IF False"].json;
// Use whichever branch executed
const result = ifTrueBranch || ifFalseBranch || {};
return [{json: result}];
```
---
## Critical: Webhook Data Structure
**MOST COMMON MISTAKE**: Forgetting webhook data is nested under `.body`
### The Problem
Webhook node wraps all incoming data under a `body` property. This catches many developers by surprise.
### Structure
```javascript
// Webhook node output structure:
{
"headers": {
"content-type": "application/json",
"user-agent": "...",
// ... other headers
},
"params": {},
"query": {},
"body": {
// ← YOUR DATA IS HERE
"name": "Alice",
"email": "alice@example.com",
"message": "Hello!"
}
}
```
### Wrong vs Right
```javascript
// ❌ WRONG: Trying to access directly
const name = $json.name; // undefined
const email = $json.email; // undefined
// ✅ CORRECT: Access via .body
const name = $json.body.name; // "Alice"
const email = $json.body.email; // "alice@example.com"
// ✅ CORRECT: Extract body first
const webhookData = $json.body;
const name = webhookData.name; // "Alice"
const email = webhookData.email; // "alice@example.com"
```
### Example: Full Webhook Processing
```javascript
// Get webhook data from previous node
const webhookOutput = $input.first().json;
// Access the actual payload
const payload = webhookOutput.body;
// Access headers if needed
const contentType = webhookOutput.headers['content-type'];
// Access query parameters if needed
const apiKey = webhookOutput.query.api_key;
// Process the actual data
return [{
json: {
// Data from webhook body
userName: payload.name,
userEmail: payload.email,
message: payload.message,
// Metadata
receivedAt: new Date().toISOString(),
contentType: contentType,
authenticated: !!apiKey
}
}];
```
### POST Data, Query Params, and Headers
```javascript
const webhook = $input.first().json;
return [{
json: {
// POST body data
formData: webhook.body,
// Query parameters (?key=value)
queryParams: webhook.query,
// HTTP headers
userAgent: webhook.headers['user-agent'],
contentType: webhook.headers['content-type'],
// Request metadata
method: webhook.method, // POST, GET, etc.
url: webhook.url
}
}];
```
### Common Webhook Scenarios
```javascript
// Scenario 1: Form submission
const formData = $json.body;
const name = formData.name;
const email = formData.email;
// Scenario 2: JSON API webhook
const apiPayload = $json.body;
const eventType = apiPayload.event;
const data = apiPayload.data;
// Scenario 3: Query parameters
const apiKey = $json.query.api_key;
const userId = $json.query.user_id;
// Scenario 4: Headers
const authorization = $json.headers['authorization'];
const signature = $json.headers['x-signature'];
```
---
## Choosing the Right Pattern
### Decision Tree
```
Do you need ALL items from previous node?
├─ YES → Use $input.all()
│
└─ NO → Do you need just the FIRST item?
├─ YES → Use $input.first()
│
└─ NO → Are you in "Each Item" mode?
├─ YES → Use $input.item
│
└─ NO → Do you need specific node data?
├─ YES → Use $node["NodeName"]
└─ NO → Use $input.first() (default)
```
### Quick Reference Table
| Scenario | Use This | Example |
|----------|----------|---------|
| Sum all amounts | `$input.all()` | `allItems.reduce((sum, i) => sum + i.json.amount, 0)` |
| Get API response | `$input.first()` | `$input.first().json.data` |
| Process each independently | `$input.item` | `$input.item.json` (Each Item mode) |
| Combine two nodes | `$node["Name"]` | `$node["API"].json` |
| Filter array | `$input.all()` | `allItems.filter(i => i.json.active)` |
| Transform single object | `$input.first()` | `{...input.first().json, new: true}` |
| Webhook data | `$input.first()` | `$input.first().json.body` |
---
## Common Mistakes
### Mistake 1: Using $json Without Context
```javascript
// ❌ WRONG: $json is ambiguous
const value = $json.field;
// ✅ CORRECT: Be explicit
const value = $input.first().json.field;
```
### Mistake 2: Forgetting .json Property
```javascript
// ❌ WRONG: Trying to access fields on item object
const items = $input.all();
const names = items.map(item => item.name); // undefined
// ✅ CORRECT: Access via .json
const names = items.map(item => item.json.name);
```
### Mistake 3: Using $input.item in All Items Mode
```javascript
// ❌ WRONG: $input.item is undefined in "All Items" mode
const data = $input.item.json; // Error!
// ✅ CORRECT: Use appropriate method
const data = $input.first().json; // Or $input.all()
```
### Mistake 4: Not Handling Empty Arrays
```javascript
// ❌ WRONG: Crashes if no items
const first = $input.all()[0].json;
// ✅ CORRECT: Check length first
const items = $input.all();
if (items.length === 0) {
return [];
}
const first = items[0].json;
// ✅ ALSO CORRECT: Use $input.first()
const first = $input.first().json; // Built-in safety
```
### Mistake 5: Modifying Original Data
```javascript
// ❌ RISKY: Mutating original
const items = $input.all();
items[0].json.modified = true; // Modifies original
return items;
// ✅ SAFE: Create new objects
const items = $input.all();
return items.map(item => ({
json: {
...item.json,
modified: true
}
}));
```
---
## Advanced Patterns
### Pattern: Pagination Handling
```javascript
const currentPage = $input.all();
const pageNumber = $node["Set Page"].json.page || 1;
// Combine with previous pages
const allPreviousPages = $node["Accumulator"]?.json.accumulated || [];
return [{
json: {
accumulated: [...allPreviousPages, ...currentPage],
currentPage: pageNumber,
totalItems: allPreviousPages.length + currentPage.length
}
}];
```
### Pattern: Conditional Node Reference
```javascript
// Access different nodes based on condition
const condition = $input.first().json.type;
let data;
if (condition === 'api') {
data = $node["API Response"].json;
} else if (condition === 'database') {
data = $node["Database"].json;
} else {
data = $node["Default"].json;
}
return [{json: data}];
```
### Pattern: Multi-Node Aggregation
```javascript
// Collect data from multiple named nodes
const sources = ['Source1', 'Source2', 'Source3'];
const allData = [];
for (const source of sources) {
const nodeData = $node[source]?.json;
if (nodeData) {
allData.push({
source,
data: nodeData
});
}
}
return allData.map(item => ({json: item}));
```
---
## Summary
**Most Common Patterns**:
1. `$input.all()` - Process multiple items, batch operations
2. `$input.first()` - Single item, API responses
3. `$input.item` - Each Item mode processing
**Critical Rule**:
- Webhook data is under `.body` property
**Best Practice**:
- Be explicit: Use `$input.first().json.field` instead of `$json.field`
- Always check for null/undefined
- Use appropriate method for your mode (All Items vs Each Item)
**See Also**:
- [SKILL.md](SKILL.md) - Overview and quick start
- [COMMON_PATTERNS.md](COMMON_PATTERNS.md) - Production patterns
- [ERROR_PATTERNS.md](ERROR_PATTERNS.md) - Avoid common mistakes

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# Error Patterns - JavaScript Code Node
Complete guide to avoiding the most common Code node errors.
---
## Overview
This guide covers the **top 5 error patterns** encountered in n8n Code nodes. Understanding and avoiding these errors will save you significant debugging time.
**Error Frequency**:
1. Empty Code / Missing Return - **38% of failures**
2. Expression Syntax Confusion - **8% of failures**
3. Incorrect Return Wrapper - **5% of failures**
4. Unmatched Expression Brackets - **6% of failures**
5. Missing Null Checks - **Common runtime error**
---
## Error #1: Empty Code or Missing Return Statement
**Frequency**: Most common error (38% of all validation failures)
**What Happens**:
- Workflow execution fails
- Next nodes receive no data
- Error: "Code cannot be empty" or "Code must return data"
### The Problem
```javascript
// ❌ ERROR: No code at all
// (Empty code field)
```
```javascript
// ❌ ERROR: Code executes but doesn't return anything
const items = $input.all();
// Process items
for (const item of items) {
console.log(item.json.name);
}
// Forgot to return!
```
```javascript
// ❌ ERROR: Early return path exists, but not all paths return
const items = $input.all();
if (items.length === 0) {
return []; // ✅ This path returns
}
// Process items
const processed = items.map(item => ({json: item.json}));
// ❌ Forgot to return processed!
```
### The Solution
```javascript
// ✅ CORRECT: Always return data
const items = $input.all();
// Process items
const processed = items.map(item => ({
json: {
...item.json,
processed: true
}
}));
return processed; // ✅ Return statement present
```
```javascript
// ✅ CORRECT: Return empty array if no items
const items = $input.all();
if (items.length === 0) {
return []; // Valid: empty array when no data
}
// Process and return
return items.map(item => ({json: item.json}));
```
```javascript
// ✅ CORRECT: All code paths return
const items = $input.all();
if (items.length === 0) {
return [];
} else if (items.length === 1) {
return [{json: {single: true, data: items[0].json}}];
} else {
return items.map(item => ({json: item.json}));
}
// All paths covered
```
### Checklist
- [ ] Code field is not empty
- [ ] Return statement exists
- [ ] ALL code paths return data (if/else branches)
- [ ] Return format is correct (`[{json: {...}}]`)
- [ ] Return happens even on errors (use try-catch)
---
## Error #2: Expression Syntax Confusion
**Frequency**: 8% of validation failures
**What Happens**:
- Syntax error in code execution
- Error: "Unexpected token" or "Expression syntax is not valid in Code nodes"
- Template variables not evaluated
### The Problem
n8n has TWO distinct syntaxes:
1. **Expression syntax** `{{ }}` - Used in OTHER nodes (Set, IF, HTTP Request)
2. **JavaScript** - Used in CODE nodes (no `{{ }}`)
Many developers mistakenly use expression syntax inside Code nodes.
```javascript
// ❌ WRONG: Using n8n expression syntax in Code node
const userName = "{{ $json.name }}";
const userEmail = "{{ $json.body.email }}";
return [{
json: {
name: userName,
email: userEmail
}
}];
// Result: Literal string "{{ $json.name }}", NOT the value!
```
```javascript
// ❌ WRONG: Trying to evaluate expressions
const value = "{{ $now.toFormat('yyyy-MM-dd') }}";
```
### The Solution
```javascript
// ✅ CORRECT: Use JavaScript directly (no {{ }})
const userName = $json.name;
const userEmail = $json.body.email;
return [{
json: {
name: userName,
email: userEmail
}
}];
```
```javascript
// ✅ CORRECT: JavaScript template literals (use backticks)
const message = `Hello, ${$json.name}! Your email is ${$json.email}`;
return [{
json: {
greeting: message
}
}];
```
```javascript
// ✅ CORRECT: Direct variable access
const item = $input.first().json;
return [{
json: {
name: item.name,
email: item.email,
timestamp: new Date().toISOString() // JavaScript Date, not {{ }}
}
}];
```
### Comparison Table
| Context | Syntax | Example |
|---------|--------|---------|
| Set node | `{{ }}` expressions | `{{ $json.name }}` |
| IF node | `{{ }}` expressions | `{{ $json.age > 18 }}` |
| HTTP Request URL | `{{ }}` expressions | `{{ $json.userId }}` |
| **Code node** | **JavaScript** | `$json.name` |
| **Code node strings** | **Template literals** | `` `Hello ${$json.name}` `` |
### Quick Fix Guide
```javascript
// WRONG → RIGHT conversions
// ❌ "{{ $json.field }}"
// ✅ $json.field
// ❌ "{{ $now }}"
// ✅ new Date().toISOString()
// ❌ "{{ $node['HTTP Request'].json.data }}"
// ✅ $node["HTTP Request"].json.data
// ❌ `{{ $json.firstName }} {{ $json.lastName }}`
// ✅ `${$json.firstName} ${$json.lastName}`
```
---
## Error #3: Incorrect Return Wrapper Format
**Frequency**: 5% of validation failures
**What Happens**:
- Error: "Return value must be an array of objects"
- Error: "Each item must have a json property"
- Next nodes receive malformed data
### The Problem
Code nodes MUST return:
- **Array** of objects
- Each object MUST have a **`json` property**
```javascript
// ❌ WRONG: Returning object instead of array
return {
json: {
result: 'success'
}
};
// Missing array wrapper []
```
```javascript
// ❌ WRONG: Returning array without json wrapper
return [
{id: 1, name: 'Alice'},
{id: 2, name: 'Bob'}
];
// Missing json property
```
```javascript
// ❌ WRONG: Returning plain value
return "processed";
```
```javascript
// ❌ WRONG: Returning items without mapping
return $input.all();
// Works if items already have json property, but not guaranteed
```
```javascript
// ❌ WRONG: Incomplete structure
return [{data: {result: 'success'}}];
// Should be {json: {...}}, not {data: {...}}
```
### The Solution
```javascript
// ✅ CORRECT: Single result
return [{
json: {
result: 'success',
timestamp: new Date().toISOString()
}
}];
```
```javascript
// ✅ CORRECT: Multiple results
return [
{json: {id: 1, name: 'Alice'}},
{json: {id: 2, name: 'Bob'}},
{json: {id: 3, name: 'Carol'}}
];
```
```javascript
// ✅ CORRECT: Transforming array
const items = $input.all();
return items.map(item => ({
json: {
id: item.json.id,
name: item.json.name,
processed: true
}
}));
```
```javascript
// ✅ CORRECT: Empty result
return [];
// Valid when no data to return
```
```javascript
// ✅ CORRECT: Conditional returns
if (shouldProcess) {
return [{json: {result: 'processed'}}];
} else {
return [];
}
```
### Return Format Checklist
- [ ] Return value is an **array** `[...]`
- [ ] Each array element has **`json` property**
- [ ] Structure is `[{json: {...}}]` or `[{json: {...}}, {json: {...}}]`
- [ ] NOT `{json: {...}}` (missing array wrapper)
- [ ] NOT `[{...}]` (missing json property)
### Common Scenarios
```javascript
// Scenario 1: Single object from API
const response = $input.first().json;
// ✅ CORRECT
return [{json: response}];
// ❌ WRONG
return {json: response};
// Scenario 2: Array of objects
const users = $input.all();
// ✅ CORRECT
return users.map(user => ({json: user.json}));
// ❌ WRONG
return users; // Risky - depends on existing structure
// Scenario 3: Computed result
const total = $input.all().reduce((sum, item) => sum + item.json.amount, 0);
// ✅ CORRECT
return [{json: {total}}];
// ❌ WRONG
return {total};
// Scenario 4: No results
// ✅ CORRECT
return [];
// ❌ WRONG
return null;
```
---
## Error #4: Unmatched Expression Brackets
**Frequency**: 6% of validation failures
**What Happens**:
- Parsing error during save
- Error: "Unmatched expression brackets"
- Code appears correct but fails validation
### The Problem
This error typically occurs when:
1. Strings contain unbalanced quotes
2. Multi-line strings with special characters
3. Template literals with nested brackets
```javascript
// ❌ WRONG: Unescaped quote in string
const message = "It's a nice day";
// Single quote breaks string
```
```javascript
// ❌ WRONG: Unbalanced brackets in regex
const pattern = /\{(\w+)\}/; // JSON storage issue
```
```javascript
// ❌ WRONG: Multi-line string with quotes
const html = "
<div class="container">
<p>Hello</p>
</div>
";
// Quote balance issues
```
### The Solution
```javascript
// ✅ CORRECT: Escape quotes
const message = "It\\'s a nice day";
// Or use different quotes
const message = "It's a nice day"; // Double quotes work
```
```javascript
// ✅ CORRECT: Escape regex properly
const pattern = /\\{(\\w+)\\}/;
```
```javascript
// ✅ CORRECT: Template literals for multi-line
const html = `
<div class="container">
<p>Hello</p>
</div>
`;
// Backticks handle multi-line and quotes
```
```javascript
// ✅ CORRECT: Escape backslashes
const path = "C:\\\\Users\\\\Documents\\\\file.txt";
```
### Escaping Guide
| Character | Escape As | Example |
|-----------|-----------|---------|
| Single quote in single-quoted string | `\\'` | `'It\\'s working'` |
| Double quote in double-quoted string | `\\"` | `"She said \\"hello\\""` |
| Backslash | `\\\\` | `"C:\\\\path"` |
| Newline | `\\n` | `"Line 1\\nLine 2"` |
| Tab | `\\t` | `"Column1\\tColumn2"` |
### Best Practices
```javascript
// ✅ BEST: Use template literals for complex strings
const message = `User ${name} said: "Hello!"`;
// ✅ BEST: Use template literals for HTML
const html = `
<div class="${className}">
<h1>${title}</h1>
<p>${content}</p>
</div>
`;
// ✅ BEST: Use template literals for JSON
const jsonString = `{
"name": "${name}",
"email": "${email}"
}`;
```
---
## Error #5: Missing Null Checks / Undefined Access
**Frequency**: Very common runtime error
**What Happens**:
- Workflow execution stops
- Error: "Cannot read property 'X' of undefined"
- Error: "Cannot read property 'X' of null"
- Crashes on missing data
### The Problem
```javascript
// ❌ WRONG: No null check - crashes if user doesn't exist
const email = item.json.user.email;
```
```javascript
// ❌ WRONG: Assumes array has items
const firstItem = $input.all()[0].json;
```
```javascript
// ❌ WRONG: Assumes nested property exists
const city = $json.address.city;
```
```javascript
// ❌ WRONG: No validation before array operations
const names = $json.users.map(user => user.name);
```
### The Solution
```javascript
// ✅ CORRECT: Optional chaining
const email = item.json?.user?.email || 'no-email@example.com';
```
```javascript
// ✅ CORRECT: Check array length
const items = $input.all();
if (items.length === 0) {
return [];
}
const firstItem = items[0].json;
```
```javascript
// ✅ CORRECT: Guard clauses
const data = $input.first().json;
if (!data.address) {
return [{json: {error: 'No address provided'}}];
}
const city = data.address.city;
```
```javascript
// ✅ CORRECT: Default values
const users = $json.users || [];
const names = users.map(user => user.name || 'Unknown');
```
```javascript
// ✅ CORRECT: Try-catch for risky operations
try {
const email = item.json.user.email.toLowerCase();
return [{json: {email}}];
} catch (error) {
return [{
json: {
error: 'Invalid user data',
details: error.message
}
}];
}
```
### Safe Access Patterns
```javascript
// Pattern 1: Optional chaining (modern, recommended)
const value = data?.nested?.property?.value;
// Pattern 2: Logical OR with default
const value = data.property || 'default';
// Pattern 3: Ternary check
const value = data.property ? data.property : 'default';
// Pattern 4: Guard clause
if (!data.property) {
return [];
}
const value = data.property;
// Pattern 5: Try-catch
try {
const value = data.nested.property.value;
} catch (error) {
const value = 'default';
}
```
### Webhook Data Safety
```javascript
// Webhook data requires extra safety
// ❌ RISKY: Assumes all fields exist
const name = $json.body.user.name;
const email = $json.body.user.email;
// ✅ SAFE: Check each level
const body = $json.body || {};
const user = body.user || {};
const name = user.name || 'Unknown';
const email = user.email || 'no-email';
// ✅ BETTER: Optional chaining
const name = $json.body?.user?.name || 'Unknown';
const email = $json.body?.user?.email || 'no-email';
```
### Array Safety
```javascript
// ❌ RISKY: No length check
const items = $input.all();
const firstId = items[0].json.id;
// ✅ SAFE: Check length
const items = $input.all();
if (items.length > 0) {
const firstId = items[0].json.id;
} else {
// Handle empty case
return [];
}
// ✅ BETTER: Use $input.first()
const firstItem = $input.first();
const firstId = firstItem.json.id; // Built-in safety
```
### Object Property Safety
```javascript
// ❌ RISKY: Direct access
const config = $json.settings.advanced.timeout;
// ✅ SAFE: Step by step with defaults
const settings = $json.settings || {};
const advanced = settings.advanced || {};
const timeout = advanced.timeout || 30000;
// ✅ BETTER: Optional chaining
const timeout = $json.settings?.advanced?.timeout ?? 30000;
// Note: ?? (nullish coalescing) vs || (logical OR)
```
---
## Error Prevention Checklist
Use this checklist before deploying Code nodes:
### Code Structure
- [ ] Code field is not empty
- [ ] Return statement exists
- [ ] All code paths return data
### Return Format
- [ ] Returns array: `[...]`
- [ ] Each item has `json` property: `{json: {...}}`
- [ ] Format is `[{json: {...}}]`
### Syntax
- [ ] No `{{ }}` expression syntax (use JavaScript)
- [ ] Template literals use backticks: `` `${variable}` ``
- [ ] All quotes and brackets balanced
- [ ] Strings properly escaped
### Data Safety
- [ ] Null checks for optional properties
- [ ] Array length checks before access
- [ ] Webhook data accessed via `.body`
- [ ] Try-catch for risky operations
- [ ] Default values for missing data
### Testing
- [ ] Test with empty input
- [ ] Test with missing fields
- [ ] Test with unexpected data types
- [ ] Check browser console for errors
---
## Quick Error Reference
| Error Message | Likely Cause | Fix |
|---------------|--------------|-----|
| "Code cannot be empty" | Empty code field | Add meaningful code |
| "Code must return data" | Missing return statement | Add `return [...]` |
| "Return value must be an array" | Returning object instead of array | Wrap in `[...]` |
| "Each item must have json property" | Missing `json` wrapper | Use `{json: {...}}` |
| "Unexpected token" | Expression syntax `{{ }}` in code | Remove `{{ }}`, use JavaScript |
| "Cannot read property X of undefined" | Missing null check | Use optional chaining `?.` |
| "Cannot read property X of null" | Null value access | Add guard clause or default |
| "Unmatched expression brackets" | Quote/bracket imbalance | Check string escaping |
---
## Debugging Tips
### 1. Use console.log()
```javascript
const items = $input.all();
console.log('Items count:', items.length);
console.log('First item:', items[0]);
// Check browser console (F12) for output
```
### 2. Return Intermediate Results
```javascript
// Debug by returning current state
const items = $input.all();
const processed = items.map(item => ({json: item.json}));
// Return to see what you have
return processed;
```
### 3. Try-Catch for Troubleshooting
```javascript
try {
// Your code here
const result = riskyOperation();
return [{json: {result}}];
} catch (error) {
// See what failed
return [{
json: {
error: error.message,
stack: error.stack
}
}];
}
```
### 4. Validate Input Structure
```javascript
const items = $input.all();
// Check what you received
console.log('Input structure:', JSON.stringify(items[0], null, 2));
// Then process
```
---
## Summary
**Top 5 Errors to Avoid**:
1. **Empty code / missing return** (38%) - Always return data
2. **Expression syntax `{{ }}`** (8%) - Use JavaScript, not expressions
3. **Wrong return format** (5%) - Always `[{json: {...}}]`
4. **Unmatched brackets** (6%) - Escape strings properly
5. **Missing null checks** - Use optional chaining `?.`
**Quick Prevention**:
- Return `[{json: {...}}]` format
- Use JavaScript, NOT `{{ }}` expressions
- Check for null/undefined before accessing
- Test with empty and invalid data
- Use browser console for debugging
**See Also**:
- [SKILL.md](SKILL.md) - Overview and best practices
- [DATA_ACCESS.md](DATA_ACCESS.md) - Safe data access patterns
- [COMMON_PATTERNS.md](COMMON_PATTERNS.md) - Working examples

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# n8n Code JavaScript
Expert guidance for writing JavaScript code in n8n Code nodes.
---
## Purpose
Teaches how to write effective JavaScript in n8n Code nodes, avoid common errors, and use built-in functions effectively.
---
## Activates On
**Trigger keywords**:
- "javascript code node"
- "write javascript in n8n"
- "code node javascript"
- "$input syntax"
- "$json syntax"
- "$helpers.httpRequest"
- "DateTime luxon"
- "code node error"
- "webhook data code"
- "return format code node"
**Common scenarios**:
- Writing JavaScript code in Code nodes
- Troubleshooting Code node errors
- Making HTTP requests from code
- Working with dates and times
- Accessing webhook data
- Choosing between All Items and Each Item mode
---
## What You'll Learn
### Quick Start
- Mode selection (All Items vs Each Item)
- Data access patterns ($input.all(), $input.first(), $input.item)
- Correct return format: `[{json: {...}}]`
- Webhook data structure (.body nesting)
- Built-in functions overview
### Data Access Mastery
- $input.all() - Batch operations (most common)
- $input.first() - Single item operations
- $input.item - Each Item mode processing
- $node - Reference other workflow nodes
- **Critical gotcha**: Webhook data under `.body`
### Common Patterns (Production-Tested)
1. Multi-source Data Aggregation
2. Regex Filtering & Pattern Matching
3. Markdown Parsing & Structured Extraction
4. JSON Comparison & Validation
5. CRM Data Transformation
6. Release Information Processing
7. Array Transformation with Context
8. Slack Block Kit Formatting
9. Top N Filtering & Ranking
10. String Aggregation & Reporting
### Error Prevention
Top 5 errors to avoid:
1. **Empty code / missing return** (38% of failures)
2. **Expression syntax confusion** (using `{{}}` in code)
3. **Incorrect return format** (missing array wrapper or json property)
4. **Unmatched brackets** (string escaping issues)
5. **Missing null checks** (crashes on undefined)
### Built-in Functions
- **$helpers.httpRequest()** - Make HTTP requests
- **DateTime (Luxon)** - Advanced date/time operations
- **$jmespath()** - Query JSON structures
- **$getWorkflowStaticData()** - Persistent storage
- Standard JavaScript globals (Math, JSON, console)
- Available Node.js modules (crypto, Buffer, URL)
---
## File Structure
```
n8n-code-javascript/
├── SKILL.md (500 lines)
│ Overview, quick start, mode selection, best practices
│ - Mode selection guide (All Items vs Each Item)
│ - Data access patterns overview
│ - Return format requirements
│ - Critical webhook gotcha
│ - Error prevention overview
│ - Quick reference checklist
│
├── DATA_ACCESS.md (400 lines)
│ Complete data access patterns
│ - $input.all() - Most common (26% usage)
│ - $input.first() - Very common (25% usage)
│ - $input.item - Each Item mode (19% usage)
│ - $node - Reference other nodes
│ - Webhook data structure (.body nesting)
│ - Choosing the right pattern
│ - Common mistakes to avoid
│
├── COMMON_PATTERNS.md (600 lines)
│ 10 production-tested patterns
│ - Pattern 1: Multi-source Aggregation
│ - Pattern 2: Regex Filtering
│ - Pattern 3: Markdown Parsing
│ - Pattern 4: JSON Comparison
│ - Pattern 5: CRM Transformation
│ - Pattern 6: Release Processing
│ - Pattern 7: Array Transformation
│ - Pattern 8: Slack Block Kit
│ - Pattern 9: Top N Filtering
│ - Pattern 10: String Aggregation
│ - Pattern selection guide
│
├── ERROR_PATTERNS.md (450 lines)
│ Top 5 errors with solutions
│ - Error #1: Empty Code / Missing Return (38%)
│ - Error #2: Expression Syntax Confusion (8%)
│ - Error #3: Incorrect Return Wrapper (5%)
│ - Error #4: Unmatched Brackets (6%)
│ - Error #5: Missing Null Checks
│ - Error prevention checklist
│ - Quick error reference
│ - Debugging tips
│
├── BUILTIN_FUNCTIONS.md (450 lines)
│ Complete built-in function reference
│ - $helpers.httpRequest() API reference
│ - DateTime (Luxon) complete guide
│ - $jmespath() JSON querying
│ - $getWorkflowStaticData() persistent storage
│ - Standard JavaScript globals
│ - Available Node.js modules
│ - What's NOT available
│
└── README.md (this file)
Skill metadata and overview
```
**Total**: ~2,400 lines across 6 files
---
## Coverage
### Mode Selection
- **Run Once for All Items** - Recommended for 95% of use cases
- **Run Once for Each Item** - Specialized cases only
- Decision guide and performance implications
### Data Access
- Most common patterns with usage statistics
- Webhook data structure (critical .body gotcha)
- Safe access patterns with null checks
- When to use which pattern
### Error Prevention
- Top 5 errors covering 62%+ of all failures
- Clear wrong vs right examples
- Error prevention checklist
- Debugging tips and console.log usage
### Production Patterns
- 10 patterns from real workflows
- Complete working examples
- Use cases and key techniques
- Pattern selection guide
### Built-in Functions
- Complete $helpers.httpRequest() reference
- DateTime/Luxon operations (formatting, parsing, arithmetic)
- $jmespath() for JSON queries
- Persistent storage with $getWorkflowStaticData()
- Standard JavaScript and Node.js modules
---
## Critical Gotchas Highlighted
### #1: Webhook Data Structure
**MOST COMMON MISTAKE**: Webhook data is under `.body`
```javascript
// ❌ WRONG
const name = $json.name;
// ✅ CORRECT
const name = $json.body.name;
```
### #2: Return Format
**CRITICAL**: Must return array with json property
```javascript
// ❌ WRONG
return {json: {result: 'success'}};
// ✅ CORRECT
return [{json: {result: 'success'}}];
```
### #3: Expression Syntax
**Don't use `{{}}` in Code nodes**
```javascript
// ❌ WRONG
const value = "{{ $json.field }}";
// ✅ CORRECT
const value = $json.field;
```
---
## Integration with Other Skills
### n8n Expression Syntax
- **Distinction**: Expressions use `{{}}` in OTHER nodes
- **Code nodes**: Use JavaScript directly (no `{{}}`)
- **When to use each**: Code vs expressions decision guide
### n8n MCP Tools Expert
- Find Code node: `search_nodes({query: "code"})`
- Get configuration: `get_node_essentials("nodes-base.code")`
- Validate code: `validate_node_operation()`
### n8n Node Configuration
- Mode selection (All Items vs Each Item)
- Language selection (JavaScript vs Python)
- Understanding property dependencies
### n8n Workflow Patterns
- Code nodes in transformation step
- Webhook → Code → API pattern
- Error handling in workflows
### n8n Validation Expert
- Validate Code node configuration
- Handle validation errors
- Auto-fix common issues
---
## When to Use Code Node
**Use Code node when:**
- ✅ Complex transformations requiring multiple steps
- ✅ Custom calculations or business logic
- ✅ Recursive operations
- ✅ API response parsing with complex structure
- ✅ Multi-step conditionals
- ✅ Data aggregation across items
**Consider other nodes when:**
- ❌ Simple field mapping → Use **Set** node
- ❌ Basic filtering → Use **Filter** node
- ❌ Simple conditionals → Use **IF** or **Switch** node
- ❌ HTTP requests only → Use **HTTP Request** node
**Code node excels at**: Complex logic that would require chaining many simple nodes
---
## Success Metrics
**Before this skill**:
- Users confused by mode selection
- Frequent return format errors
- Expression syntax mistakes
- Webhook data access failures
- Missing null check crashes
**After this skill**:
- Clear mode selection guidance
- Understanding of return format
- JavaScript vs expression distinction
- Correct webhook data access
- Safe null-handling patterns
- Production-ready code patterns
---
## Quick Reference
### Essential Rules
1. Choose "All Items" mode (recommended)
2. Access data: `$input.all()`, `$input.first()`, `$input.item`
3. **MUST return**: `[{json: {...}}]` format
4. **Webhook data**: Under `.body` property
5. **No `{{}}` syntax**: Use JavaScript directly
### Most Common Patterns
- Batch processing → $input.all() + map/filter
- Single item → $input.first()
- Aggregation → reduce()
- HTTP requests → $helpers.httpRequest()
- Date handling → DateTime (Luxon)
### Error Prevention
- Always return data
- Check for null/undefined
- Use try-catch for risky operations
- Test with empty input
- Use console.log() for debugging
---
## Related Documentation
- **n8n Code Node Guide**: https://docs.n8n.io/code/code-node/
- **Built-in Methods Reference**: https://docs.n8n.io/code-examples/methods-variables-reference/
- **Luxon Documentation**: https://moment.github.io/luxon/
---
## Evaluations
**5 test scenarios** covering:
1. Webhook body gotcha (most common mistake)
2. Return format error (missing array wrapper)
3. HTTP request with $helpers.httpRequest()
4. Aggregation pattern with $input.all()
5. Expression syntax confusion (using `{{}}`)
Each evaluation tests skill activation, correct guidance, and reference to appropriate documentation files.
---
## Version History
- **v1.0** (2025-01-20): Initial implementation
- SKILL.md with comprehensive overview
- DATA_ACCESS.md covering all access patterns
- COMMON_PATTERNS.md with 10 production patterns
- ERROR_PATTERNS.md covering top 5 errors
- BUILTIN_FUNCTIONS.md complete reference
- 5 evaluation scenarios
---
## Author
Conceived by Romuald Członkowski - [www.aiadvisors.pl/en](https://www.aiadvisors.pl/en)
Part of the n8n-skills collection.

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---
name: n8n-code-javascript
description: Write JavaScript code in n8n Code nodes. Use when writing JavaScript in n8n, using $input/$json/$node syntax, making HTTP requests with $helpers, working with dates using DateTime, troubleshooting Code node errors, or choosing between Code node modes.
---
# JavaScript Code Node
Expert guidance for writing JavaScript code in n8n Code nodes.
---
## Quick Start
```javascript
// Basic template for Code nodes
const items = $input.all();
// Process data
const processed = items.map(item => ({
json: {
...item.json,
processed: true,
timestamp: new Date().toISOString()
}
}));
return processed;
```
### Essential Rules
1. **Choose "Run Once for All Items" mode** (recommended for most use cases)
2. **Access data**: `$input.all()`, `$input.first()`, or `$input.item`
3. **CRITICAL**: Must return `[{json: {...}}]` format
4. **CRITICAL**: Webhook data is under `$json.body` (not `$json` directly)
5. **Built-ins available**: $helpers.httpRequest(), DateTime (Luxon), $jmespath()
---
## Mode Selection Guide
The Code node offers two execution modes. Choose based on your use case:
### Run Once for All Items (Recommended - Default)
**Use this mode for:** 95% of use cases
- **How it works**: Code executes **once** regardless of input count
- **Data access**: `$input.all()` or `items` array
- **Best for**: Aggregation, filtering, batch processing, transformations, API calls with all data
- **Performance**: Faster for multiple items (single execution)
```javascript
// Example: Calculate total from all items
const allItems = $input.all();
const total = allItems.reduce((sum, item) => sum + (item.json.amount || 0), 0);
return [{
json: {
total,
count: allItems.length,
average: total / allItems.length
}
}];
```
**When to use:**
- ✅ Comparing items across the dataset
- ✅ Calculating totals, averages, or statistics
- ✅ Sorting or ranking items
- ✅ Deduplication
- ✅ Building aggregated reports
- ✅ Combining data from multiple items
### Run Once for Each Item
**Use this mode for:** Specialized cases only
- **How it works**: Code executes **separately** for each input item
- **Data access**: `$input.item` or `$item`
- **Best for**: Item-specific logic, independent operations, per-item validation
- **Performance**: Slower for large datasets (multiple executions)
```javascript
// Example: Add processing timestamp to each item
const item = $input.item;
return [{
json: {
...item.json,
processed: true,
processedAt: new Date().toISOString()
}
}];
```
**When to use:**
- ✅ Each item needs independent API call
- ✅ Per-item validation with different error handling
- ✅ Item-specific transformations based on item properties
- ✅ When items must be processed separately for business logic
**Decision Shortcut:**
- **Need to look at multiple items?** → Use "All Items" mode
- **Each item completely independent?** → Use "Each Item" mode
- **Not sure?** → Use "All Items" mode (you can always loop inside)
---
## Data Access Patterns
### Pattern 1: $input.all() - Most Common
**Use when**: Processing arrays, batch operations, aggregations
```javascript
// Get all items from previous node
const allItems = $input.all();
// Filter, map, reduce as needed
const valid = allItems.filter(item => item.json.status === 'active');
const mapped = valid.map(item => ({
json: {
id: item.json.id,
name: item.json.name
}
}));
return mapped;
```
### Pattern 2: $input.first() - Very Common
**Use when**: Working with single objects, API responses, first-in-first-out
```javascript
// Get first item only
const firstItem = $input.first();
const data = firstItem.json;
return [{
json: {
result: processData(data),
processedAt: new Date().toISOString()
}
}];
```
### Pattern 3: $input.item - Each Item Mode Only
**Use when**: In "Run Once for Each Item" mode
```javascript
// Current item in loop (Each Item mode only)
const currentItem = $input.item;
return [{
json: {
...currentItem.json,
itemProcessed: true
}
}];
```
### Pattern 4: $node - Reference Other Nodes
**Use when**: Need data from specific nodes in workflow
```javascript
// Get output from specific node
const webhookData = $node["Webhook"].json;
const httpData = $node["HTTP Request"].json;
return [{
json: {
combined: {
webhook: webhookData,
api: httpData
}
}
}];
```
**See**: [DATA_ACCESS.md](DATA_ACCESS.md) for comprehensive guide
---
## Critical: Webhook Data Structure
**MOST COMMON MISTAKE**: Webhook data is nested under `.body`
```javascript
// ❌ WRONG - Will return undefined
const name = $json.name;
const email = $json.email;
// ✅ CORRECT - Webhook data is under .body
const name = $json.body.name;
const email = $json.body.email;
// Or with $input
const webhookData = $input.first().json.body;
const name = webhookData.name;
```
**Why**: Webhook node wraps all request data under `body` property. This includes POST data, query parameters, and JSON payloads.
**See**: [DATA_ACCESS.md](DATA_ACCESS.md) for full webhook structure details
---
## Return Format Requirements
**CRITICAL RULE**: Always return array of objects with `json` property
### Correct Return Formats
```javascript
// ✅ Single result
return [{
json: {
field1: value1,
field2: value2
}
}];
// ✅ Multiple results
return [
{json: {id: 1, data: 'first'}},
{json: {id: 2, data: 'second'}}
];
// ✅ Transformed array
const transformed = $input.all()
.filter(item => item.json.valid)
.map(item => ({
json: {
id: item.json.id,
processed: true
}
}));
return transformed;
// ✅ Empty result (when no data to return)
return [];
// ✅ Conditional return
if (shouldProcess) {
return [{json: processedData}];
} else {
return [];
}
```
### Incorrect Return Formats
```javascript
// ❌ WRONG: Object without array wrapper
return {
json: {field: value}
};
// ❌ WRONG: Array without json wrapper
return [{field: value}];
// ❌ WRONG: Plain string
return "processed";
// ❌ WRONG: Raw data without mapping
return $input.all(); // Missing .map()
// ❌ WRONG: Incomplete structure
return [{data: value}]; // Should be {json: value}
```
**Why it matters**: Next nodes expect array format. Incorrect format causes workflow execution to fail.
**See**: [ERROR_PATTERNS.md](ERROR_PATTERNS.md) #3 for detailed error solutions
---
## Common Patterns Overview
Based on production workflows, here are the most useful patterns:
### 1. Multi-Source Data Aggregation
Combine data from multiple APIs, webhooks, or nodes
```javascript
const allItems = $input.all();
const results = [];
for (const item of allItems) {
const sourceName = item.json.name || 'Unknown';
// Parse source-specific structure
if (sourceName === 'API1' && item.json.data) {
results.push({
json: {
title: item.json.data.title,
source: 'API1'
}
});
}
}
return results;
```
### 2. Filtering with Regex
Extract patterns, mentions, or keywords from text
```javascript
const pattern = /\b([A-Z]{2,5})\b/g;
const matches = {};
for (const item of $input.all()) {
const text = item.json.text;
const found = text.match(pattern);
if (found) {
found.forEach(match => {
matches[match] = (matches[match] || 0) + 1;
});
}
}
return [{json: {matches}}];
```
### 3. Data Transformation & Enrichment
Map fields, normalize formats, add computed fields
```javascript
const items = $input.all();
return items.map(item => {
const data = item.json;
const nameParts = data.name.split(' ');
return {
json: {
first_name: nameParts[0],
last_name: nameParts.slice(1).join(' '),
email: data.email,
created_at: new Date().toISOString()
}
};
});
```
### 4. Top N Filtering & Ranking
Sort and limit results
```javascript
const items = $input.all();
const topItems = items
.sort((a, b) => (b.json.score || 0) - (a.json.score || 0))
.slice(0, 10);
return topItems.map(item => ({json: item.json}));
```
### 5. Aggregation & Reporting
Sum, count, group data
```javascript
const items = $input.all();
const total = items.reduce((sum, item) => sum + (item.json.amount || 0), 0);
return [{
json: {
total,
count: items.length,
average: total / items.length,
timestamp: new Date().toISOString()
}
}];
```
**See**: [COMMON_PATTERNS.md](COMMON_PATTERNS.md) for 10 detailed production patterns
---
## Error Prevention - Top 5 Mistakes
### #1: Empty Code or Missing Return (Most Common)
```javascript
// ❌ WRONG: No return statement
const items = $input.all();
// ... processing code ...
// Forgot to return!
// ✅ CORRECT: Always return data
const items = $input.all();
// ... processing ...
return items.map(item => ({json: item.json}));
```
### #2: Expression Syntax Confusion
```javascript
// ❌ WRONG: Using n8n expression syntax in code
const value = "{{ $json.field }}";
// ✅ CORRECT: Use JavaScript template literals
const value = `${$json.field}`;
// ✅ CORRECT: Direct access
const value = $input.first().json.field;
```
### #3: Incorrect Return Wrapper
```javascript
// ❌ WRONG: Returning object instead of array
return {json: {result: 'success'}};
// ✅ CORRECT: Array wrapper required
return [{json: {result: 'success'}}];
```
### #4: Missing Null Checks
```javascript
// ❌ WRONG: Crashes if field doesn't exist
const value = item.json.user.email;
// ✅ CORRECT: Safe access with optional chaining
const value = item.json?.user?.email || 'no-email@example.com';
// ✅ CORRECT: Guard clause
if (!item.json.user) {
return [];
}
const value = item.json.user.email;
```
### #5: Webhook Body Nesting
```javascript
// ❌ WRONG: Direct access to webhook data
const email = $json.email;
// ✅ CORRECT: Webhook data under .body
const email = $json.body.email;
```
**See**: [ERROR_PATTERNS.md](ERROR_PATTERNS.md) for comprehensive error guide
---
## Built-in Functions & Helpers
### $helpers.httpRequest()
Make HTTP requests from within code:
```javascript
const response = await $helpers.httpRequest({
method: 'GET',
url: 'https://api.example.com/data',
headers: {
'Authorization': 'Bearer token',
'Content-Type': 'application/json'
}
});
return [{json: {data: response}}];
```
### DateTime (Luxon)
Date and time operations:
```javascript
// Current time
const now = DateTime.now();
// Format dates
const formatted = now.toFormat('yyyy-MM-dd');
const iso = now.toISO();
// Date arithmetic
const tomorrow = now.plus({days: 1});
const lastWeek = now.minus({weeks: 1});
return [{
json: {
today: formatted,
tomorrow: tomorrow.toFormat('yyyy-MM-dd')
}
}];
```
### $jmespath()
Query JSON structures:
```javascript
const data = $input.first().json;
// Filter array
const adults = $jmespath(data, 'users[?age >= `18`]');
// Extract fields
const names = $jmespath(data, 'users[*].name');
return [{json: {adults, names}}];
```
**See**: [BUILTIN_FUNCTIONS.md](BUILTIN_FUNCTIONS.md) for complete reference
---
## Best Practices
### 1. Always Validate Input Data
```javascript
const items = $input.all();
// Check if data exists
if (!items || items.length === 0) {
return [];
}
// Validate structure
if (!items[0].json) {
return [{json: {error: 'Invalid input format'}}];
}
// Continue processing...
```
### 2. Use Try-Catch for Error Handling
```javascript
try {
const response = await $helpers.httpRequest({
url: 'https://api.example.com/data'
});
return [{json: {success: true, data: response}}];
} catch (error) {
return [{
json: {
success: false,
error: error.message
}
}];
}
```
### 3. Prefer Array Methods Over Loops
```javascript
// ✅ GOOD: Functional approach
const processed = $input.all()
.filter(item => item.json.valid)
.map(item => ({json: {id: item.json.id}}));
// ❌ SLOWER: Manual loop
const processed = [];
for (const item of $input.all()) {
if (item.json.valid) {
processed.push({json: {id: item.json.id}});
}
}
```
### 4. Filter Early, Process Late
```javascript
// ✅ GOOD: Filter first to reduce processing
const processed = $input.all()
.filter(item => item.json.status === 'active') // Reduce dataset first
.map(item => expensiveTransformation(item)); // Then transform
// ❌ WASTEFUL: Transform everything, then filter
const processed = $input.all()
.map(item => expensiveTransformation(item)) // Wastes CPU
.filter(item => item.json.status === 'active');
```
### 5. Use Descriptive Variable Names
```javascript
// ✅ GOOD: Clear intent
const activeUsers = $input.all().filter(item => item.json.active);
const totalRevenue = activeUsers.reduce((sum, user) => sum + user.json.revenue, 0);
// ❌ BAD: Unclear purpose
const a = $input.all().filter(item => item.json.active);
const t = a.reduce((s, u) => s + u.json.revenue, 0);
```
### 6. Debug with console.log()
```javascript
// Debug statements appear in browser console
const items = $input.all();
console.log(`Processing ${items.length} items`);
for (const item of items) {
console.log('Item data:', item.json);
// Process...
}
return result;
```
---
## When to Use Code Node
Use Code node when:
- ✅ Complex transformations requiring multiple steps
- ✅ Custom calculations or business logic
- ✅ Recursive operations
- ✅ API response parsing with complex structure
- ✅ Multi-step conditionals
- ✅ Data aggregation across items
Consider other nodes when:
- ❌ Simple field mapping → Use **Set** node
- ❌ Basic filtering → Use **Filter** node
- ❌ Simple conditionals → Use **IF** or **Switch** node
- ❌ HTTP requests only → Use **HTTP Request** node
**Code node excels at**: Complex logic that would require chaining many simple nodes
---
## Integration with Other Skills
### Works With:
**n8n Expression Syntax**:
- Expressions use `{{ }}` syntax in other nodes
- Code nodes use JavaScript directly (no `{{ }}`)
- When to use expressions vs code
**n8n MCP Tools Expert**:
- How to find Code node: `search_nodes({query: "code"})`
- Get configuration help: `get_node_essentials("nodes-base.code")`
- Validate code: `validate_node_operation()`
**n8n Node Configuration**:
- Mode selection (All Items vs Each Item)
- Language selection (JavaScript vs Python)
- Understanding property dependencies
**n8n Workflow Patterns**:
- Code nodes in transformation step
- Webhook → Code → API pattern
- Error handling in workflows
**n8n Validation Expert**:
- Validate Code node configuration
- Handle validation errors
- Auto-fix common issues
---
## Quick Reference Checklist
Before deploying Code nodes, verify:
- [ ] **Code is not empty** - Must have meaningful logic
- [ ] **Return statement exists** - Must return array of objects
- [ ] **Proper return format** - Each item: `{json: {...}}`
- [ ] **Data access correct** - Using `$input.all()`, `$input.first()`, or `$input.item`
- [ ] **No n8n expressions** - Use JavaScript template literals: `` `${value}` ``
- [ ] **Error handling** - Guard clauses for null/undefined inputs
- [ ] **Webhook data** - Access via `.body` if from webhook
- [ ] **Mode selection** - "All Items" for most cases
- [ ] **Performance** - Prefer map/filter over manual loops
- [ ] **Output consistent** - All code paths return same structure
---
## Additional Resources
### Related Files
- [DATA_ACCESS.md](DATA_ACCESS.md) - Comprehensive data access patterns
- [COMMON_PATTERNS.md](COMMON_PATTERNS.md) - 10 production-tested patterns
- [ERROR_PATTERNS.md](ERROR_PATTERNS.md) - Top 5 errors and solutions
- [BUILTIN_FUNCTIONS.md](BUILTIN_FUNCTIONS.md) - Complete built-in reference
### n8n Documentation
- Code Node Guide: https://docs.n8n.io/code/code-node/
- Built-in Methods: https://docs.n8n.io/code-examples/methods-variables-reference/
- Luxon Documentation: https://moment.github.io/luxon/
---
**Ready to write JavaScript in n8n Code nodes!** Start with simple transformations, use the error patterns guide to avoid common mistakes, and reference the pattern library for production-ready examples.

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# Property Dependencies Guide
Deep dive into n8n property dependencies and displayOptions mechanism.
---
## What Are Property Dependencies?
**Definition**: Rules that control when fields are visible or required based on other field values.
**Mechanism**: `displayOptions` in node schema
**Purpose**:
- Show relevant fields only
- Hide irrelevant fields
- Simplify configuration UX
- Prevent invalid configurations
---
## displayOptions Structure
### Basic Format
```javascript
{
"name": "fieldName",
"type": "string",
"displayOptions": {
"show": {
"otherField": ["value1", "value2"]
}
}
}
```
**Translation**: Show `fieldName` when `otherField` equals "value1" OR "value2"
### Show vs Hide
#### show (Most Common)
**Show field when condition matches**:
```javascript
{
"name": "body",
"displayOptions": {
"show": {
"sendBody": [true]
}
}
}
```
**Meaning**: Show `body` when `sendBody = true`
#### hide (Less Common)
**Hide field when condition matches**:
```javascript
{
"name": "advanced",
"displayOptions": {
"hide": {
"simpleMode": [true]
}
}
}
```
**Meaning**: Hide `advanced` when `simpleMode = true`
### Multiple Conditions (AND Logic)
```javascript
{
"name": "body",
"displayOptions": {
"show": {
"sendBody": [true],
"method": ["POST", "PUT", "PATCH"]
}
}
}
```
**Meaning**: Show `body` when:
- `sendBody = true` AND
- `method IN (POST, PUT, PATCH)`
**All conditions must match** (AND logic)
### Multiple Values (OR Logic)
```javascript
{
"name": "someField",
"displayOptions": {
"show": {
"method": ["POST", "PUT", "PATCH"]
}
}
}
```
**Meaning**: Show `someField` when:
- `method = POST` OR
- `method = PUT` OR
- `method = PATCH`
**Any value matches** (OR logic)
---
## Common Dependency Patterns
### Pattern 1: Boolean Toggle
**Use case**: Optional feature flag
**Example**: HTTP Request sendBody
```javascript
// Field: sendBody (boolean)
{
"name": "sendBody",
"type": "boolean",
"default": false
}
// Field: body (depends on sendBody)
{
"name": "body",
"displayOptions": {
"show": {
"sendBody": [true]
}
}
}
```
**Flow**:
1. User sees sendBody checkbox
2. When checked → body field appears
3. When unchecked → body field hides
### Pattern 2: Resource/Operation Cascade
**Use case**: Different operations show different fields
**Example**: Slack message operations
```javascript
// Operation: post
{
"name": "channel",
"displayOptions": {
"show": {
"resource": ["message"],
"operation": ["post"]
}
}
}
// Operation: update
{
"name": "messageId",
"displayOptions": {
"show": {
"resource": ["message"],
"operation": ["update"]
}
}
}
```
**Flow**:
1. User selects resource="message"
2. User selects operation="post" → sees channel
3. User changes to operation="update" → channel hides, messageId shows
### Pattern 3: Type-Specific Configuration
**Use case**: Different types need different fields
**Example**: IF node conditions
```javascript
// String operations
{
"name": "value2",
"displayOptions": {
"show": {
"conditions.string.0.operation": ["equals", "notEquals", "contains"]
}
}
}
// Unary operations (isEmpty) don't show value2
{
"displayOptions": {
"hide": {
"conditions.string.0.operation": ["isEmpty", "isNotEmpty"]
}
}
}
```
### Pattern 4: Method-Specific Fields
**Use case**: HTTP methods have different options
**Example**: HTTP Request
```javascript
// Query parameters (all methods can have)
{
"name": "queryParameters",
"displayOptions": {
"show": {
"sendQuery": [true]
}
}
}
// Body (only certain methods)
{
"name": "body",
"displayOptions": {
"show": {
"sendBody": [true],
"method": ["POST", "PUT", "PATCH", "DELETE"]
}
}
}
```
---
## Using get_property_dependencies
### Basic Usage
```javascript
const deps = get_property_dependencies({
nodeType: "nodes-base.httpRequest"
});
```
### Example Response
```javascript
{
"nodeType": "n8n-nodes-base.httpRequest",
"dependencies": {
"body": {
"shows_when": {
"sendBody": [true],
"method": ["POST", "PUT", "PATCH", "DELETE"]
},
"required_when_shown": true
},
"queryParameters": {
"shows_when": {
"sendQuery": [true]
},
"required_when_shown": false
},
"headerParameters": {
"shows_when": {
"sendHeaders": [true]
},
"required_when_shown": false
}
}
}
```
### When to Use
**✅ Use when**:
- Validation fails with "missing field" but you don't see that field
- A field appears/disappears unexpectedly
- You need to understand what controls field visibility
- Building dynamic configuration tools
**❌ Don't use when**:
- Simple configuration (use get_node_essentials)
- Just starting configuration
- Field requirements are obvious
---
## Complex Dependency Examples
### Example 1: HTTP Request Complete Flow
**Scenario**: Configuring POST with JSON body
**Step 1**: Set method
```javascript
{
"method": "POST"
// → sendBody becomes visible
}
```
**Step 2**: Enable body
```javascript
{
"method": "POST",
"sendBody": true
// → body field becomes visible AND required
}
```
**Step 3**: Configure body
```javascript
{
"method": "POST",
"sendBody": true,
"body": {
"contentType": "json"
// → content field becomes visible AND required
}
}
```
**Step 4**: Add content
```javascript
{
"method": "POST",
"sendBody": true,
"body": {
"contentType": "json",
"content": {
"name": "John",
"email": "john@example.com"
}
}
}
// ✅ Valid!
```
**Dependency chain**:
```
method=POST
→ sendBody visible
→ sendBody=true
→ body visible + required
→ body.contentType=json
→ body.content visible + required
```
### Example 2: IF Node Operator Dependencies
**Scenario**: String comparison with different operators
**Binary operator** (equals):
```javascript
{
"conditions": {
"string": [
{
"operation": "equals"
// → value1 required
// → value2 required
// → singleValue should NOT be set
}
]
}
}
```
**Unary operator** (isEmpty):
```javascript
{
"conditions": {
"string": [
{
"operation": "isEmpty"
// → value1 required
// → value2 should NOT be set
// → singleValue should be true (auto-added)
}
]
}
}
```
**Dependency table**:
| Operator | value1 | value2 | singleValue |
|---|---|---|---|
| equals | Required | Required | false |
| notEquals | Required | Required | false |
| contains | Required | Required | false |
| isEmpty | Required | Hidden | true |
| isNotEmpty | Required | Hidden | true |
### Example 3: Slack Operation Matrix
**Scenario**: Different Slack operations show different fields
```javascript
// post message
{
"resource": "message",
"operation": "post"
// Shows: channel (required), text (required), attachments, blocks
}
// update message
{
"resource": "message",
"operation": "update"
// Shows: messageId (required), text (required), channel (optional)
}
// delete message
{
"resource": "message",
"operation": "delete"
// Shows: messageId (required), channel (required)
// Hides: text, attachments, blocks
}
// get message
{
"resource": "message",
"operation": "get"
// Shows: messageId (required), channel (required)
// Hides: text, attachments, blocks
}
```
**Field visibility matrix**:
| Field | post | update | delete | get |
|---|---|---|---|---|
| channel | Required | Optional | Required | Required |
| text | Required | Required | Hidden | Hidden |
| messageId | Hidden | Required | Required | Required |
| attachments | Optional | Optional | Hidden | Hidden |
| blocks | Optional | Optional | Hidden | Hidden |
---
## Nested Dependencies
### What Are They?
**Definition**: Dependencies within object properties
**Example**: HTTP Request body.contentType controls body.content structure
```javascript
{
"body": {
"contentType": "json",
// → content expects JSON object
"content": {
"key": "value"
}
}
}
{
"body": {
"contentType": "form-data",
// → content expects form fields array
"content": [
{
"name": "field1",
"value": "value1"
}
]
}
}
```
### How to Handle
**Strategy**: Configure parent first, then children
```javascript
// Step 1: Parent
{
"body": {
"contentType": "json" // Set parent first
}
}
// Step 2: Children (structure determined by parent)
{
"body": {
"contentType": "json",
"content": { // JSON object format
"key": "value"
}
}
}
```
---
## Auto-Sanitization and Dependencies
### What Auto-Sanitization Fixes
**Operator structure issues** (IF/Switch nodes):
**Example**: singleValue property
```javascript
// You configure (missing singleValue)
{
"type": "boolean",
"operation": "isEmpty"
// Missing singleValue
}
// Auto-sanitization adds it
{
"type": "boolean",
"operation": "isEmpty",
"singleValue": true // ✅ Added automatically
}
```
### What It Doesn't Fix
**Missing required fields**:
```javascript
// You configure (missing channel)
{
"resource": "message",
"operation": "post",
"text": "Hello"
// Missing required field: channel
}
// Auto-sanitization does NOT add
// You must add it yourself
{
"resource": "message",
"operation": "post",
"channel": "#general", // ← You must add
"text": "Hello"
}
```
---
## Troubleshooting Dependencies
### Problem 1: "Field X is required but not visible"
**Error**:
```json
{
"type": "missing_required",
"property": "body",
"message": "body is required"
}
```
**But you don't see body field in configuration!**
**Solution**:
```javascript
// Check dependencies
const deps = get_property_dependencies({
nodeType: "nodes-base.httpRequest"
});
// Find that body shows when sendBody=true
// Add sendBody
{
"method": "POST",
"sendBody": true, // ← Now body appears!
"body": {...}
}
```
### Problem 2: "Field disappears when I change operation"
**Scenario**:
```javascript
// Working configuration
{
"resource": "message",
"operation": "post",
"channel": "#general",
"text": "Hello"
}
// Change operation
{
"resource": "message",
"operation": "update", // Changed
"channel": "#general", // Still here
"text": "Updated" // Still here
// Missing: messageId (required for update!)
}
```
**Validation error**: "messageId is required"
**Why**: Different operation = different required fields
**Solution**:
```javascript
// Check essentials for new operation
get_node_essentials({
nodeType: "nodes-base.slack"
});
// Configure for update operation
{
"resource": "message",
"operation": "update",
"messageId": "1234567890", // Required for update
"text": "Updated",
"channel": "#general" // Optional for update
}
```
### Problem 3: "Validation passes but field doesn't save"
**Scenario**: Field hidden by dependencies after validation
**Example**:
```javascript
// Configure
{
"method": "GET",
"sendBody": true, // ❌ GET doesn't support body
"body": {...} // This will be stripped
}
// After save
{
"method": "GET"
// body removed because method=GET hides it
}
```
**Solution**: Respect dependencies from the start
```javascript
// Correct approach
get_property_dependencies({
nodeType: "nodes-base.httpRequest"
});
// See that body only shows for POST/PUT/PATCH/DELETE
// Use correct method
{
"method": "POST",
"sendBody": true,
"body": {...}
}
```
---
## Advanced Patterns
### Pattern 1: Conditional Required with Fallback
**Example**: Channel can be string OR expression
```javascript
// Option 1: String
{
"channel": "#general"
}
// Option 2: Expression
{
"channel": "={{$json.channelName}}"
}
// Validation accepts both
```
### Pattern 2: Mutually Exclusive Fields
**Example**: Use either ID or name, not both
```javascript
// Use messageId
{
"messageId": "1234567890"
// name not needed
}
// OR use messageName
{
"messageName": "thread-name"
// messageId not needed
}
// Dependencies ensure only one is required
```
### Pattern 3: Progressive Complexity
**Example**: Simple mode vs advanced mode
```javascript
// Simple mode
{
"mode": "simple",
"text": "{{$json.message}}"
// Advanced fields hidden
}
// Advanced mode
{
"mode": "advanced",
"attachments": [...],
"blocks": [...],
"metadata": {...}
// Simple field hidden, advanced fields shown
}
```
---
## Best Practices
### ✅ Do
1. **Check dependencies when stuck**
```javascript
get_property_dependencies({nodeType: "..."});
```
2. **Configure parent properties first**
```javascript
// First: method, resource, operation
// Then: dependent fields
```
3. **Validate after changing operation**
```javascript
// Operation changed → requirements changed
validate_node_operation({...});
```
4. **Read validation errors for dependency hints**
```
Error: "body required when sendBody=true"
→ Hint: Set sendBody=true to enable body
```
### ❌ Don't
1. **Don't ignore dependency errors**
```javascript
// Error: "body not visible" → Check displayOptions
```
2. **Don't hardcode all possible fields**
```javascript
// Bad: Adding fields that will be hidden
```
3. **Don't assume operations are identical**
```javascript
// Each operation has unique requirements
```
---
## Summary
**Key Concepts**:
- `displayOptions` control field visibility
- `show` = field appears when conditions match
- `hide` = field disappears when conditions match
- Multiple conditions = AND logic
- Multiple values = OR logic
**Common Patterns**:
1. Boolean toggle (sendBody → body)
2. Resource/operation cascade (different operations → different fields)
3. Type-specific config (string vs boolean conditions)
4. Method-specific fields (GET vs POST)
**Troubleshooting**:
- Field required but not visible → Check dependencies
- Field disappears after change → Operation changed requirements
- Field doesn't save → Hidden by dependencies
**Tools**:
- `get_property_dependencies` - See dependency rules
- `get_node_essentials` - See operation requirements
- Validation errors - Hints about dependencies
**Related Files**:
- **[SKILL.md](SKILL.md)** - Main configuration guide
- **[OPERATION_PATTERNS.md](OPERATION_PATTERNS.md)** - Common patterns by node type

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# Operation Patterns Guide
Common node configuration patterns organized by node type and operation.
---
## Overview
**Purpose**: Quick reference for common node configurations
**Coverage**: Top 20 most-used nodes from 525 available
**Pattern format**:
- Minimal valid configuration
- Common options
- Real-world examples
- Gotchas and tips
---
## HTTP & API Nodes
### HTTP Request (nodes-base.httpRequest)
Most versatile node for HTTP operations
#### GET Request
**Minimal**:
```javascript
{
"method": "GET",
"url": "https://api.example.com/users",
"authentication": "none"
}
```
**With query parameters**:
```javascript
{
"method": "GET",
"url": "https://api.example.com/users",
"authentication": "none",
"sendQuery": true,
"queryParameters": {
"parameters": [
{
"name": "limit",
"value": "100"
},
{
"name": "offset",
"value": "={{$json.offset}}"
}
]
}
}
```
**With authentication**:
```javascript
{
"method": "GET",
"url": "https://api.example.com/users",
"authentication": "predefinedCredentialType",
"nodeCredentialType": "httpHeaderAuth"
}
```
#### POST with JSON
**Minimal**:
```javascript
{
"method": "POST",
"url": "https://api.example.com/users",
"authentication": "none",
"sendBody": true,
"body": {
"contentType": "json",
"content": {
"name": "John Doe",
"email": "john@example.com"
}
}
}
```
**With expressions**:
```javascript
{
"method": "POST",
"url": "https://api.example.com/users",
"authentication": "none",
"sendBody": true,
"body": {
"contentType": "json",
"content": {
"name": "={{$json.name}}",
"email": "={{$json.email}}",
"metadata": {
"source": "n8n",
"timestamp": "={{$now.toISO()}}"
}
}
}
}
```
**Gotcha**: Remember `sendBody: true` for POST/PUT/PATCH!
#### PUT/PATCH Request
**Pattern**: Same as POST, but method changes
```javascript
{
"method": "PUT", // or "PATCH"
"url": "https://api.example.com/users/123",
"authentication": "none",
"sendBody": true,
"body": {
"contentType": "json",
"content": {
"name": "Updated Name"
}
}
}
```
#### DELETE Request
**Minimal** (no body):
```javascript
{
"method": "DELETE",
"url": "https://api.example.com/users/123",
"authentication": "none"
}
```
**With body** (some APIs allow):
```javascript
{
"method": "DELETE",
"url": "https://api.example.com/users",
"authentication": "none",
"sendBody": true,
"body": {
"contentType": "json",
"content": {
"ids": ["123", "456"]
}
}
}
```
---
### Webhook (nodes-base.webhook)
Most common trigger - 813 searches!
#### Basic Webhook
**Minimal**:
```javascript
{
"path": "my-webhook",
"httpMethod": "POST",
"responseMode": "onReceived"
}
```
**Gotcha**: Webhook data is under `$json.body`, not `$json`!
```javascript
// ❌ Wrong
{
"text": "={{$json.email}}"
}
// ✅ Correct
{
"text": "={{$json.body.email}}"
}
```
#### Webhook with Authentication
**Header auth**:
```javascript
{
"path": "secure-webhook",
"httpMethod": "POST",
"responseMode": "onReceived",
"authentication": "headerAuth",
"options": {
"responseCode": 200,
"responseData": "{\n \"success\": true\n}"
}
}
```
#### Webhook Returning Data
**Custom response**:
```javascript
{
"path": "my-webhook",
"httpMethod": "POST",
"responseMode": "lastNode", // Return data from last node
"options": {
"responseCode": 201,
"responseHeaders": {
"entries": [
{
"name": "Content-Type",
"value": "application/json"
}
]
}
}
}
```
---
## Communication Nodes
### Slack (nodes-base.slack)
Popular choice for AI agent workflows
#### Post Message
**Minimal**:
```javascript
{
"resource": "message",
"operation": "post",
"channel": "#general",
"text": "Hello from n8n!"
}
```
**With dynamic content**:
```javascript
{
"resource": "message",
"operation": "post",
"channel": "={{$json.channel}}",
"text": "New user: {{$json.name}} ({{$json.email}})"
}
```
**With attachments**:
```javascript
{
"resource": "message",
"operation": "post",
"channel": "#alerts",
"text": "Error Alert",
"attachments": [
{
"color": "#ff0000",
"fields": [
{
"title": "Error Type",
"value": "={{$json.errorType}}"
},
{
"title": "Timestamp",
"value": "={{$now.toLocaleString()}}"
}
]
}
]
}
```
**Gotcha**: Channel must start with `#` for public channels or be a channel ID!
#### Update Message
**Minimal**:
```javascript
{
"resource": "message",
"operation": "update",
"messageId": "1234567890.123456", // From previous message post
"text": "Updated message content"
}
```
**Note**: `messageId` required, `channel` optional (can be inferred)
#### Create Channel
**Minimal**:
```javascript
{
"resource": "channel",
"operation": "create",
"name": "new-project-channel", // Lowercase, no spaces
"isPrivate": false
}
```
**Gotcha**: Channel name must be lowercase, no spaces, 1-80 chars!
---
### Gmail (nodes-base.gmail)
Popular for email automation
#### Send Email
**Minimal**:
```javascript
{
"resource": "message",
"operation": "send",
"to": "user@example.com",
"subject": "Hello from n8n",
"message": "This is the email body"
}
```
**With dynamic content**:
```javascript
{
"resource": "message",
"operation": "send",
"to": "={{$json.email}}",
"subject": "Order Confirmation #{{$json.orderId}}",
"message": "Dear {{$json.name}},\n\nYour order has been confirmed.\n\nThank you!",
"options": {
"ccList": "admin@example.com",
"replyTo": "support@example.com"
}
}
```
#### Get Email
**Minimal**:
```javascript
{
"resource": "message",
"operation": "getAll",
"returnAll": false,
"limit": 10
}
```
**With filters**:
```javascript
{
"resource": "message",
"operation": "getAll",
"returnAll": false,
"limit": 50,
"filters": {
"q": "is:unread from:important@example.com",
"labelIds": ["INBOX"]
}
}
```
---
## Database Nodes
### Postgres (nodes-base.postgres)
Database operations - 456 templates
#### Execute Query
**Minimal** (SELECT):
```javascript
{
"operation": "executeQuery",
"query": "SELECT * FROM users WHERE active = true LIMIT 100"
}
```
**With parameters** (SQL injection prevention):
```javascript
{
"operation": "executeQuery",
"query": "SELECT * FROM users WHERE email = $1 AND active = $2",
"additionalFields": {
"mode": "list",
"queryParameters": "user@example.com,true"
}
}
```
**Gotcha**: ALWAYS use parameterized queries for user input!
```javascript
// ❌ BAD - SQL injection risk!
{
"query": "SELECT * FROM users WHERE email = '{{$json.email}}'"
}
// ✅ GOOD - Parameterized
{
"query": "SELECT * FROM users WHERE email = $1",
"additionalFields": {
"mode": "list",
"queryParameters": "={{$json.email}}"
}
}
```
#### Insert
**Minimal**:
```javascript
{
"operation": "insert",
"table": "users",
"columns": "name,email,created_at",
"additionalFields": {
"mode": "list",
"queryParameters": "John Doe,john@example.com,NOW()"
}
}
```
**With expressions**:
```javascript
{
"operation": "insert",
"table": "users",
"columns": "name,email,metadata",
"additionalFields": {
"mode": "list",
"queryParameters": "={{$json.name}},={{$json.email}},{{JSON.stringify($json)}}"
}
}
```
#### Update
**Minimal**:
```javascript
{
"operation": "update",
"table": "users",
"updateKey": "id",
"columns": "name,email",
"additionalFields": {
"mode": "list",
"queryParameters": "={{$json.id}},Updated Name,newemail@example.com"
}
}
```
---
## Data Transformation Nodes
### Set (nodes-base.set)
Most used transformation - 68% of workflows!
#### Set Fixed Values
**Minimal**:
```javascript
{
"mode": "manual",
"duplicateItem": false,
"assignments": {
"assignments": [
{
"name": "status",
"value": "active",
"type": "string"
},
{
"name": "count",
"value": 100,
"type": "number"
}
]
}
}
```
#### Set from Input Data
**Mapping data**:
```javascript
{
"mode": "manual",
"duplicateItem": false,
"assignments": {
"assignments": [
{
"name": "fullName",
"value": "={{$json.firstName}} {{$json.lastName}}",
"type": "string"
},
{
"name": "email",
"value": "={{$json.email.toLowerCase()}}",
"type": "string"
},
{
"name": "timestamp",
"value": "={{$now.toISO()}}",
"type": "string"
}
]
}
}
```
**Gotcha**: Use correct `type` for each field!
```javascript
// ❌ Wrong type
{
"name": "age",
"value": "25", // String
"type": "string" // Will be string "25"
}
// ✅ Correct type
{
"name": "age",
"value": 25, // Number
"type": "number" // Will be number 25
}
```
---
### Code (nodes-base.code)
JavaScript execution - 42% of workflows
#### Simple Transformation
**Minimal**:
```javascript
{
"mode": "runOnceForAllItems",
"jsCode": "return $input.all().map(item => ({\n json: {\n name: item.json.name.toUpperCase(),\n email: item.json.email\n }\n}));"
}
```
**Per-item processing**:
```javascript
{
"mode": "runOnceForEachItem",
"jsCode": "// Process each item\nconst data = $input.item.json;\n\nreturn {\n json: {\n fullName: `${data.firstName} ${data.lastName}`,\n email: data.email.toLowerCase(),\n timestamp: new Date().toISOString()\n }\n};"
}
```
**Gotcha**: In Code nodes, use `$input.item.json` or `$input.all()`, NOT `{{...}}`!
```javascript
// ❌ Wrong - expressions don't work in Code nodes
{
"jsCode": "const name = '={{$json.name}}';"
}
// ✅ Correct - direct access
{
"jsCode": "const name = $input.item.json.name;"
}
```
---
## Conditional Nodes
### IF (nodes-base.if)
Conditional logic - 38% of workflows
#### String Comparison
**Equals** (binary):
```javascript
{
"conditions": {
"string": [
{
"value1": "={{$json.status}}",
"operation": "equals",
"value2": "active"
}
]
}
}
```
**Contains** (binary):
```javascript
{
"conditions": {
"string": [
{
"value1": "={{$json.email}}",
"operation": "contains",
"value2": "@example.com"
}
]
}
}
```
**isEmpty** (unary):
```javascript
{
"conditions": {
"string": [
{
"value1": "={{$json.email}}",
"operation": "isEmpty"
// No value2 - unary operator
// singleValue: true added by auto-sanitization
}
]
}
}
```
**Gotcha**: Unary operators (isEmpty, isNotEmpty) don't need value2!
#### Number Comparison
**Greater than**:
```javascript
{
"conditions": {
"number": [
{
"value1": "={{$json.age}}",
"operation": "larger",
"value2": 18
}
]
}
}
```
#### Boolean Comparison
**Is true**:
```javascript
{
"conditions": {
"boolean": [
{
"value1": "={{$json.isActive}}",
"operation": "true"
// Unary - no value2
}
]
}
}
```
#### Multiple Conditions (AND)
**All must match**:
```javascript
{
"conditions": {
"string": [
{
"value1": "={{$json.status}}",
"operation": "equals",
"value2": "active"
}
],
"number": [
{
"value1": "={{$json.age}}",
"operation": "larger",
"value2": 18
}
]
},
"combineOperation": "all" // AND logic
}
```
#### Multiple Conditions (OR)
**Any can match**:
```javascript
{
"conditions": {
"string": [
{
"value1": "={{$json.status}}",
"operation": "equals",
"value2": "active"
},
{
"value1": "={{$json.status}}",
"operation": "equals",
"value2": "pending"
}
]
},
"combineOperation": "any" // OR logic
}
```
---
### Switch (nodes-base.switch)
Multi-way routing - 18% of workflows
#### Basic Switch
**Minimal**:
```javascript
{
"mode": "rules",
"rules": {
"rules": [
{
"conditions": {
"string": [
{
"value1": "={{$json.status}}",
"operation": "equals",
"value2": "active"
}
]
}
},
{
"conditions": {
"string": [
{
"value1": "={{$json.status}}",
"operation": "equals",
"value2": "pending"
}
]
}
}
]
},
"fallbackOutput": "extra" // Catch-all for non-matching
}
```
**Gotcha**: Number of rules must match number of outputs!
---
## AI Nodes
### OpenAI (nodes-langchain.openAi)
AI operations - 234 templates
#### Chat Completion
**Minimal**:
```javascript
{
"resource": "chat",
"operation": "complete",
"messages": {
"values": [
{
"role": "user",
"content": "={{$json.prompt}}"
}
]
}
}
```
**With system prompt**:
```javascript
{
"resource": "chat",
"operation": "complete",
"messages": {
"values": [
{
"role": "system",
"content": "You are a helpful assistant specialized in customer support."
},
{
"role": "user",
"content": "={{$json.userMessage}}"
}
]
},
"options": {
"temperature": 0.7,
"maxTokens": 500
}
}
```
---
## Schedule Nodes
### Schedule Trigger (nodes-base.scheduleTrigger)
Time-based workflows - 28% have schedule triggers
#### Daily at Specific Time
**Minimal**:
```javascript
{
"rule": {
"interval": [
{
"field": "hours",
"hoursInterval": 24
}
],
"hour": 9,
"minute": 0,
"timezone": "America/New_York"
}
}
```
**Gotcha**: Always set timezone explicitly!
```javascript
// ❌ Bad - uses server timezone
{
"rule": {
"interval": [...]
}
}
// ✅ Good - explicit timezone
{
"rule": {
"interval": [...],
"timezone": "America/New_York"
}
}
```
#### Every N Minutes
**Minimal**:
```javascript
{
"rule": {
"interval": [
{
"field": "minutes",
"minutesInterval": 15
}
]
}
}
```
#### Cron Expression
**Advanced scheduling**:
```javascript
{
"mode": "cron",
"cronExpression": "0 */2 * * *", // Every 2 hours
"timezone": "America/New_York"
}
```
---
## Summary
**Key Patterns by Category**:
| Category | Most Common | Key Gotcha |
|---|---|---|
| HTTP/API | GET, POST JSON | Remember sendBody: true |
| Webhooks | POST receiver | Data under $json.body |
| Communication | Slack post | Channel format (#name) |
| Database | SELECT with params | Use parameterized queries |
| Transform | Set assignments | Correct type per field |
| Conditional | IF string equals | Unary vs binary operators |
| AI | OpenAI chat | System + user messages |
| Schedule | Daily at time | Set timezone explicitly |
**Configuration Approach**:
1. Use patterns as starting point
2. Adapt to your use case
3. Validate configuration
4. Iterate based on errors
5. Deploy when valid
**Related Files**:
- **[SKILL.md](SKILL.md)** - Configuration workflow and philosophy
- **[DEPENDENCIES.md](DEPENDENCIES.md)** - Property dependency rules

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# n8n Node Configuration
Expert guidance for operation-aware node configuration with property dependencies.
## Overview
**Skill Name**: n8n Node Configuration
**Priority**: Medium
**Purpose**: Teach operation-aware configuration with progressive discovery and dependency awareness
## The Problem This Solves
Node configuration patterns:
- get_node_essentials is the primary discovery tool (18s avg from search → essentials)
- 91.7% success rate with essentials-based configuration
- 56 seconds average between configuration edits
**Key insight**: Most configurations only need essentials, not full schema!
## What This Skill Teaches
### Core Concepts
1. **Operation-Aware Configuration**
- Resource + operation determine required fields
- Different operations = different requirements
- Always check requirements when changing operation
2. **Property Dependencies**
- Fields appear/disappear based on other field values
- displayOptions control visibility
- Conditional required fields
- Understanding dependency chains
3. **Progressive Discovery**
- Start with get_node_essentials (91.7% success)
- Escalate to get_property_dependencies if needed
- Use get_node_info only when necessary
- Right tool for right job
4. **Configuration Workflow**
- Identify → Discover → Configure → Validate → Iterate
- Average 2-3 validation cycles
- Read errors for dependency hints
- 56 seconds between edits average
5. **Common Patterns**
- Resource/operation nodes (Slack, Sheets)
- HTTP-based nodes (HTTP Request, Webhook)
- Database nodes (Postgres, MySQL)
- Conditional logic nodes (IF, Switch)
## File Structure
```
n8n-node-configuration/
├── SKILL.md (692 lines)
│ Main configuration guide
│ - Configuration philosophy (progressive disclosure)
│ - Core concepts (operation-aware, dependencies)
│ - Configuration workflow (8-step process)
│ - get_node_essentials vs get_node_info
│ - Property dependencies deep dive
│ - Common node patterns (4 categories)
│ - Operation-specific examples
│ - Conditional requirements
│ - Anti-patterns and best practices
│
├── DEPENDENCIES.md (671 lines)
│ Property dependencies reference
│ - displayOptions mechanism
│ - show vs hide rules
│ - Multiple conditions (AND logic)
│ - Multiple values (OR logic)
│ - 4 common dependency patterns
│ - Using get_property_dependencies
│ - Complex dependency examples
│ - Nested dependencies
│ - Auto-sanitization interaction
│ - Troubleshooting guide
│ - Advanced patterns
│
├── OPERATION_PATTERNS.md (783 lines)
│ Common configurations by node type
│ - HTTP Request (GET/POST/PUT/DELETE)
│ - Webhook (basic/auth/response)
│ - Slack (post/update/create)
│ - Gmail (send/get)
│ - Postgres (query/insert/update)
│ - Set (values/mapping)
│ - Code (per-item/all-items)
│ - IF (string/number/boolean)
│ - Switch (rules/fallback)
│ - OpenAI (chat completion)
│ - Schedule (daily/interval/cron)
│ - Gotchas and tips for each
│
└── README.md (this file)
Skill metadata and statistics
```
**Total**: ~2,146 lines across 4 files + 4 evaluations
## Usage Statistics
Configuration metrics:
| Metric | Value | Insight |
|---|---|---|
| get_node_essentials | Primary tool | Most popular discovery pattern |
| Success rate (essentials) | 91.7% | Essentials sufficient for most |
| Avg time search→essentials | 18 seconds | Fast discovery workflow |
| Avg time between edits | 56 seconds | Iterative configuration |
## Tool Usage Pattern
**Most common discovery pattern**:
```
search_nodes → get_node_essentials (18s average)
```
**Configuration cycle**:
```
get_node_essentials → configure → validate → iterate (56s avg per edit)
```
## Key Insights
### 1. Progressive Disclosure Works
**91.7% success rate** with get_node_essentials proves most configurations don't need full schema.
**Strategy**:
1. Start with essentials
2. Escalate to dependencies if stuck
3. Use full schema only when necessary
### 2. Operations Determine Requirements
**Same node, different operation = different requirements**
Example: Slack message
- `operation="post"` → needs channel + text
- `operation="update"` → needs messageId + text (different!)
### 3. Dependencies Control Visibility
**Fields appear/disappear based on other values**
Example: HTTP Request
- `method="GET"` → body hidden
- `method="POST"` + `sendBody=true` → body required
### 4. Configuration is Iterative
**Average 56 seconds between edits** shows configuration is iterative, not one-shot.
**Normal workflow**:
1. Configure minimal
2. Validate → error
3. Add missing field
4. Validate → error
5. Adjust value
6. Validate → valid ✅
### 5. Common Gotchas Exist
**Top 5 gotchas** from patterns:
1. Webhook data under `$json.body` (not `$json`)
2. POST needs `sendBody: true`
3. Slack channel format (`#name`)
4. SQL parameterized queries (injection prevention)
5. Timezone must be explicit (schedule nodes)
## Usage Examples
### Example 1: Basic Configuration Flow
```javascript
// Step 1: Get essentials
const info = get_node_essentials({
nodeType: "nodes-base.slack"
});
// Step 2: Configure for operation
{
"resource": "message",
"operation": "post",
"channel": "#general",
"text": "Hello!"
}
// Step 3: Validate
validate_node_operation({...});
// ✅ Valid!
```
### Example 2: Handling Dependencies
```javascript
// Step 1: Configure HTTP POST
{
"method": "POST",
"url": "https://api.example.com/create"
}
// Step 2: Validate → Error: "sendBody required"
// Step 3: Check dependencies
get_property_dependencies({
nodeType: "nodes-base.httpRequest"
});
// Shows: body visible when sendBody=true
// Step 4: Fix
{
"method": "POST",
"url": "https://api.example.com/create",
"sendBody": true,
"body": {
"contentType": "json",
"content": {...}
}
}
// ✅ Valid!
```
### Example 3: Operation Change
```javascript
// Initial config (post operation)
{
"resource": "message",
"operation": "post",
"channel": "#general",
"text": "Hello"
}
// Change operation
{
"resource": "message",
"operation": "update", // Changed!
// Need to check new requirements
}
// Get essentials for update operation
get_node_essentials({nodeType: "nodes-base.slack"});
// Shows: messageId required, channel optional
// Correct config
{
"resource": "message",
"operation": "update",
"messageId": "1234567890.123456",
"text": "Updated"
}
```
## When This Skill Activates
**Trigger phrases**:
- "how to configure"
- "what fields are required"
- "property dependencies"
- "get_node_essentials vs get_node_info"
- "operation-specific"
- "field not visible"
**Common scenarios**:
- Configuring new nodes
- Understanding required fields
- Field appears/disappears unexpectedly
- Choosing between discovery tools
- Switching operations
- Learning common patterns
## Integration with Other Skills
### Works With:
- **n8n MCP Tools Expert** - How to call discovery tools correctly
- **n8n Validation Expert** - Interpret missing_required errors
- **n8n Expression Syntax** - Configure expression fields
- **n8n Workflow Patterns** - Apply patterns with proper node config
### Complementary:
- Use MCP Tools Expert to learn tool selection
- Use Validation Expert to fix configuration errors
- Use Expression Syntax for dynamic field values
- Use Workflow Patterns to understand node relationships
## Testing
**Evaluations**: 4 test scenarios
1. **eval-001-property-dependencies.json**
- Tests understanding of displayOptions
- Guides to get_property_dependencies
- Explains conditional requirements
2. **eval-002-operation-specific-config.json**
- Tests operation-aware configuration
- Identifies resource + operation pattern
- References OPERATION_PATTERNS.md
3. **eval-003-conditional-fields.json**
- Tests unary vs binary operators
- Explains singleValue dependency
- Mentions auto-sanitization
4. **eval-004-essentials-vs-info.json**
- Tests tool selection knowledge
- Explains progressive disclosure
- Provides success rate statistics
## Success Metrics
**Before this skill**:
- Using get_node_info for everything (slow, overwhelming)
- Not understanding property dependencies
- Confused when fields appear/disappear
- Not aware of operation-specific requirements
- Trial and error configuration
**After this skill**:
- Start with get_node_essentials (91.7% success)
- Understand displayOptions mechanism
- Predict field visibility based on dependencies
- Check requirements when changing operations
- Systematic configuration approach
- Know common patterns by node type
## Coverage
**Node types covered**: Top 20 most-used nodes
| Category | Nodes | Coverage |
|---|---|---|
| HTTP/API | HTTP Request, Webhook | Complete |
| Communication | Slack, Gmail | Common operations |
| Database | Postgres, MySQL | CRUD operations |
| Transform | Set, Code | All modes |
| Conditional | IF, Switch | All operator types |
| AI | OpenAI | Chat completion |
| Schedule | Schedule Trigger | All modes |
## Related Documentation
- **n8n-mcp MCP Server**: Provides discovery tools
- **n8n Node API**: get_node_essentials, get_property_dependencies, get_node_info
- **n8n Schema**: displayOptions mechanism, property definitions
## Version History
- **v1.0** (2025-10-20): Initial implementation
- SKILL.md with configuration workflow
- DEPENDENCIES.md with displayOptions deep dive
- OPERATION_PATTERNS.md with 20+ node patterns
- 4 evaluation scenarios
## Author
Conceived by Romuald Członkowski - [www.aiadvisors.pl/en](https://www.aiadvisors.pl/en)
Part of the n8n-skills meta-skill collection.

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---
name: n8n-node-configuration
description: Operation-aware node configuration guidance. Use when configuring nodes, understanding property dependencies, determining required fields, choosing between get_node_essentials and get_node_info, or learning common configuration patterns by node type.
---
# n8n Node Configuration
Expert guidance for operation-aware node configuration with property dependencies.
---
## Configuration Philosophy
**Progressive disclosure**: Start minimal, add complexity as needed
Configuration best practices:
- get_node_essentials is the most used discovery pattern
- 56 seconds average between configuration edits
- 91.7% success rate with essentials-based configuration
**Key insight**: Most configurations need only essentials, not full schema!
---
## Core Concepts
### 1. Operation-Aware Configuration
**Not all fields are always required** - it depends on operation!
**Example**: Slack node
```javascript
// For operation='post'
{
"resource": "message",
"operation": "post",
"channel": "#general", // Required for post
"text": "Hello!" // Required for post
}
// For operation='update'
{
"resource": "message",
"operation": "update",
"messageId": "123", // Required for update (different!)
"text": "Updated!" // Required for update
// channel NOT required for update
}
```
**Key**: Resource + operation determine which fields are required!
### 2. Property Dependencies
**Fields appear/disappear based on other field values**
**Example**: HTTP Request node
```javascript
// When method='GET'
{
"method": "GET",
"url": "https://api.example.com"
// sendBody not shown (GET doesn't have body)
}
// When method='POST'
{
"method": "POST",
"url": "https://api.example.com",
"sendBody": true, // Now visible!
"body": { // Required when sendBody=true
"contentType": "json",
"content": {...}
}
}
```
**Mechanism**: displayOptions control field visibility
### 3. Progressive Discovery
**Use the right tool for the right job**:
1. **get_node_essentials** (91.7% success rate)
- Quick overview
- Required fields
- Common options
- **Use first** - covers 90% of needs
2. **get_property_dependencies** (for complex nodes)
- Shows what fields depend on others
- Reveals conditional requirements
- Use when essentials isn't enough
3. **get_node_info** (full schema)
- Complete documentation
- All possible fields
- Use when essentials + dependencies insufficient
---
## Configuration Workflow
### Standard Process
```
1. Identify node type and operation
↓
2. Use get_node_essentials
↓
3. Configure required fields
↓
4. Validate configuration
↓
5. If dependencies unclear → get_property_dependencies
↓
6. Add optional fields as needed
↓
7. Validate again
↓
8. Deploy
```
### Example: Configuring HTTP Request
**Step 1**: Identify what you need
```javascript
// Goal: POST JSON to API
```
**Step 2**: Get essentials
```javascript
const info = get_node_essentials({
nodeType: "nodes-base.httpRequest"
});
// Returns: method, url, sendBody, body, authentication required/optional
```
**Step 3**: Minimal config
```javascript
{
"method": "POST",
"url": "https://api.example.com/create",
"authentication": "none"
}
```
**Step 4**: Validate
```javascript
validate_node_operation({
nodeType: "nodes-base.httpRequest",
config,
profile: "runtime"
});
// → Error: "sendBody required for POST"
```
**Step 5**: Add required field
```javascript
{
"method": "POST",
"url": "https://api.example.com/create",
"authentication": "none",
"sendBody": true
}
```
**Step 6**: Validate again
```javascript
validate_node_operation({...});
// → Error: "body required when sendBody=true"
```
**Step 7**: Complete configuration
```javascript
{
"method": "POST",
"url": "https://api.example.com/create",
"authentication": "none",
"sendBody": true,
"body": {
"contentType": "json",
"content": {
"name": "={{$json.name}}",
"email": "={{$json.email}}"
}
}
}
```
**Step 8**: Final validation
```javascript
validate_node_operation({...});
// → Valid! ✅
```
---
## get_node_essentials vs get_node_info
### Use get_node_essentials When:
**✅ Starting configuration** (91.7% success rate)
```javascript
get_node_essentials({
nodeType: "nodes-base.slack"
});
```
**Returns**:
- Required fields
- Common options
- Basic examples
- Operation list
**Fast**: ~18 seconds average (from search → essentials)
### Use get_node_info When:
**✅ Essentials insufficient**
```javascript
get_node_info({
nodeType: "nodes-base.slack"
});
```
**Returns**:
- Full schema
- All properties
- Complete documentation
- Advanced options
**Slower**: More data to process
### Decision Tree
```
┌─────────────────────────────────┐
│ Starting new node config? │
├─────────────────────────────────┤
│ YES → get_node_essentials │
└─────────────────────────────────┘
↓
┌─────────────────────────────────┐
│ Essentials has what you need? │
├─────────────────────────────────┤
│ YES → Configure with essentials │
│ NO → Continue │
└─────────────────────────────────┘
↓
┌─────────────────────────────────┐
│ Need dependency info? │
├─────────────────────────────────┤
│ YES → get_property_dependencies │
│ NO → Continue │
└─────────────────────────────────┘
↓
┌─────────────────────────────────┐
│ Still need more details? │
├─────────────────────────────────┤
│ YES → get_node_info │
└─────────────────────────────────┘
```
---
## Property Dependencies Deep Dive
### displayOptions Mechanism
**Fields have visibility rules**:
```javascript
{
"name": "body",
"displayOptions": {
"show": {
"sendBody": [true],
"method": ["POST", "PUT", "PATCH"]
}
}
}
```
**Translation**: "body" field shows when:
- sendBody = true AND
- method = POST, PUT, or PATCH
### Common Dependency Patterns
#### Pattern 1: Boolean Toggle
**Example**: HTTP Request sendBody
```javascript
// sendBody controls body visibility
{
"sendBody": true // → body field appears
}
```
#### Pattern 2: Operation Switch
**Example**: Slack resource/operation
```javascript
// Different operations → different fields
{
"resource": "message",
"operation": "post"
// → Shows: channel, text, attachments, etc.
}
{
"resource": "message",
"operation": "update"
// → Shows: messageId, text (different fields!)
}
```
#### Pattern 3: Type Selection
**Example**: IF node conditions
```javascript
{
"type": "string",
"operation": "contains"
// → Shows: value1, value2
}
{
"type": "boolean",
"operation": "equals"
// → Shows: value1, value2, different operators
}
```
### Using get_property_dependencies
**Example**:
```javascript
const deps = get_property_dependencies({
nodeType: "nodes-base.httpRequest"
});
// Returns dependency tree
{
"dependencies": {
"body": {
"shows_when": {
"sendBody": [true],
"method": ["POST", "PUT", "PATCH", "DELETE"]
}
},
"queryParameters": {
"shows_when": {
"sendQuery": [true]
}
}
}
}
```
**Use this when**: Validation fails and you don't understand why field is missing/required
---
## Common Node Patterns
### Pattern 1: Resource/Operation Nodes
**Examples**: Slack, Google Sheets, Airtable
**Structure**:
```javascript
{
"resource": "<entity>", // What type of thing
"operation": "<action>", // What to do with it
// ... operation-specific fields
}
```
**How to configure**:
1. Choose resource
2. Choose operation
3. Use get_node_essentials to see operation-specific requirements
4. Configure required fields
### Pattern 2: HTTP-Based Nodes
**Examples**: HTTP Request, Webhook
**Structure**:
```javascript
{
"method": "<HTTP_METHOD>",
"url": "<endpoint>",
"authentication": "<type>",
// ... method-specific fields
}
```
**Dependencies**:
- POST/PUT/PATCH → sendBody available
- sendBody=true → body required
- authentication != "none" → credentials required
### Pattern 3: Database Nodes
**Examples**: Postgres, MySQL, MongoDB
**Structure**:
```javascript
{
"operation": "<query|insert|update|delete>",
// ... operation-specific fields
}
```
**Dependencies**:
- operation="executeQuery" → query required
- operation="insert" → table + values required
- operation="update" → table + values + where required
### Pattern 4: Conditional Logic Nodes
**Examples**: IF, Switch, Merge
**Structure**:
```javascript
{
"conditions": {
"<type>": [
{
"operation": "<operator>",
"value1": "...",
"value2": "..." // Only for binary operators
}
]
}
}
```
**Dependencies**:
- Binary operators (equals, contains, etc.) → value1 + value2
- Unary operators (isEmpty, isNotEmpty) → value1 only + singleValue: true
---
## Operation-Specific Configuration
### Slack Node Examples
#### Post Message
```javascript
{
"resource": "message",
"operation": "post",
"channel": "#general", // Required
"text": "Hello!", // Required
"attachments": [], // Optional
"blocks": [] // Optional
}
```
#### Update Message
```javascript
{
"resource": "message",
"operation": "update",
"messageId": "1234567890", // Required (different from post!)
"text": "Updated!", // Required
"channel": "#general" // Optional (can be inferred)
}
```
#### Create Channel
```javascript
{
"resource": "channel",
"operation": "create",
"name": "new-channel", // Required
"isPrivate": false // Optional
// Note: text NOT required for this operation
}
```
### HTTP Request Node Examples
#### GET Request
```javascript
{
"method": "GET",
"url": "https://api.example.com/users",
"authentication": "predefinedCredentialType",
"nodeCredentialType": "httpHeaderAuth",
"sendQuery": true, // Optional
"queryParameters": { // Shows when sendQuery=true
"parameters": [
{
"name": "limit",
"value": "100"
}
]
}
}
```
#### POST with JSON
```javascript
{
"method": "POST",
"url": "https://api.example.com/users",
"authentication": "none",
"sendBody": true, // Required for POST
"body": { // Required when sendBody=true
"contentType": "json",
"content": {
"name": "John Doe",
"email": "john@example.com"
}
}
}
```
### IF Node Examples
#### String Comparison (Binary)
```javascript
{
"conditions": {
"string": [
{
"value1": "={{$json.status}}",
"operation": "equals",
"value2": "active" // Binary: needs value2
}
]
}
}
```
#### Empty Check (Unary)
```javascript
{
"conditions": {
"string": [
{
"value1": "={{$json.email}}",
"operation": "isEmpty",
// No value2 - unary operator
"singleValue": true // Auto-added by sanitization
}
]
}
}
```
---
## Handling Conditional Requirements
### Example: HTTP Request Body
**Scenario**: body field required, but only sometimes
**Rule**:
```
body is required when:
- sendBody = true AND
- method IN (POST, PUT, PATCH, DELETE)
```
**How to discover**:
```javascript
// Option 1: Read validation error
validate_node_operation({...});
// Error: "body required when sendBody=true"
// Option 2: Check dependencies
get_property_dependencies({
nodeType: "nodes-base.httpRequest"
});
// Shows: body → shows_when: sendBody=[true], method=[POST,PUT,PATCH,DELETE]
// Option 3: Try minimal config and iterate
// Start without body, validation will tell you if needed
```
### Example: IF Node singleValue
**Scenario**: singleValue property appears for unary operators
**Rule**:
```
singleValue should be true when:
- operation IN (isEmpty, isNotEmpty, true, false)
```
**Good news**: Auto-sanitization fixes this!
**Manual check**:
```javascript
get_property_dependencies({
nodeType: "nodes-base.if"
});
// Shows operator-specific dependencies
```
---
## Configuration Anti-Patterns
### ❌ Don't: Over-configure Upfront
**Bad**:
```javascript
// Adding every possible field
{
"method": "GET",
"url": "...",
"sendQuery": false,
"sendHeaders": false,
"sendBody": false,
"timeout": 10000,
"ignoreResponseCode": false,
// ... 20 more optional fields
}
```
**Good**:
```javascript
// Start minimal
{
"method": "GET",
"url": "...",
"authentication": "none"
}
// Add fields only when needed
```
### ❌ Don't: Skip Validation
**Bad**:
```javascript
// Configure and deploy without validating
const config = {...};
n8n_update_partial_workflow({...}); // YOLO
```
**Good**:
```javascript
// Validate before deploying
const config = {...};
const result = validate_node_operation({...});
if (result.valid) {
n8n_update_partial_workflow({...});
}
```
### ❌ Don't: Ignore Operation Context
**Bad**:
```javascript
// Same config for all Slack operations
{
"resource": "message",
"operation": "post",
"channel": "#general",
"text": "..."
}
// Then switching operation without updating config
{
"resource": "message",
"operation": "update", // Changed
"channel": "#general", // Wrong field for update!
"text": "..."
}
```
**Good**:
```javascript
// Check requirements when changing operation
get_node_essentials({
nodeType: "nodes-base.slack"
});
// See what update operation needs (messageId, not channel)
```
---
## Best Practices
### ✅ Do
1. **Start with get_node_essentials**
- 91.7% success rate
- Faster than get_node_info
- Sufficient for most needs
2. **Validate iteratively**
- Configure → Validate → Fix → Repeat
- Average 2-3 iterations is normal
- Read validation errors carefully
3. **Use property dependencies when stuck**
- If field seems missing, check dependencies
- Understand what controls field visibility
- get_property_dependencies reveals rules
4. **Respect operation context**
- Different operations = different requirements
- Always check essentials when changing operation
- Don't assume configs are transferable
5. **Trust auto-sanitization**
- Operator structure fixed automatically
- Don't manually add/remove singleValue
- IF/Switch metadata added on save
### ❌ Don't
1. **Jump to get_node_info immediately**
- Try essentials first
- Only escalate if needed
- Full schema is overwhelming
2. **Configure blindly**
- Always validate before deploying
- Understand why fields are required
- Check dependencies for conditional fields
3. **Copy configs without understanding**
- Different operations need different fields
- Validate after copying
- Adjust for new context
4. **Manually fix auto-sanitization issues**
- Let auto-sanitization handle operator structure
- Focus on business logic
- Save and let system fix structure
---
## Detailed References
For comprehensive guides on specific topics:
- **[DEPENDENCIES.md](DEPENDENCIES.md)** - Deep dive into property dependencies and displayOptions
- **[OPERATION_PATTERNS.md](OPERATION_PATTERNS.md)** - Common configuration patterns by node type
---
## Summary
**Configuration Strategy**:
1. Start with get_node_essentials (91.7% success)
2. Configure required fields for operation
3. Validate configuration
4. Check dependencies if stuck
5. Iterate until valid (avg 2-3 cycles)
6. Deploy with confidence
**Key Principles**:
- **Operation-aware**: Different operations = different requirements
- **Progressive disclosure**: Start minimal, add as needed
- **Dependency-aware**: Understand field visibility rules
- **Validation-driven**: Let validation guide configuration
**Related Skills**:
- **n8n MCP Tools Expert** - How to use discovery tools correctly
- **n8n Validation Expert** - Interpret validation errors
- **n8n Expression Syntax** - Configure expression fields
- **n8n Workflow Patterns** - Apply patterns with proper configuration