Initial commit

2025-11-29 18:17:17 +08:00
commit 6062d3994e
39 changed files with 21748 additions and 0 deletions
--- a/skills/n8n-code-javascript/SKILL.md
+++ b/skills/n8n-code-javascript/SKILL.md
@@ -0,0 +1,699 @@
+---
+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.