Now liveThe Skillselion MCP - thousands of ranked skills, loaded into your agent mid-task. No install.Get it →
aaaaqwq avatar

N8n Code Javascript

aaaaqwq/claude-code-skills

  • 7 installs
  • 82 repo stars
  • Updated August 2, 2026
  • aaaaqwq/claude-code-skills

n8n-code-javascript is a Claude Code skill that guides writing JavaScript in n8n Code nodes.

About

n8n-code-javascript is a Claude Code skill that guides writing JavaScript inside n8n Code nodes. It covers the two execution modes, data-access patterns with $input, $json and $node, the required array-of-json return format, and common errors like webhook payloads nested under .body. A developer uses it when building or debugging JavaScript logic in an n8n workflow.

  • Reference for writing JavaScript in n8n Code nodes using $input/$json/$node syntax
  • Explains the two Code node modes and when to use each
  • Flags common mistakes like webhook data nested under .body and required return format

N8n Code Javascript by the numbers

  • 7 all-time installs (skills.sh)
  • Ranked #1,590 of 2,719 Automation & Workflows skills by installs in the Skillselion catalog
  • Data as of Aug 3, 2026 (Skillselion catalog sync)
At a glance

n8n-code-javascript capabilities & compatibility

Capabilities
workflow automation · code generation · data transformation
Works with
n8n
From the docs

What n8n-code-javascript says it does

**MOST COMMON MISTAKE**: Webhook data is nested under `.body`
SKILL.md
Choose "Run Once for All Items" mode
SKILL.md
npx skills add https://github.com/aaaaqwq/claude-code-skills --skill n8n-code-javascript

Add your badge

Show developers this skill is listed on Skillselion. Paste this into your README.

Listed on Skillselion
Installs7
repo stars★ 82
Last updatedAugust 2, 2026
Repositoryaaaaqwq/claude-code-skills ↗

What it does

Write and debug JavaScript inside n8n Code nodes with correct data access and return formats.

When should I use this skill?

The user writes JavaScript in an n8n Code node or hits a Code node error.

By the numbers

  • 4 documented data-access patterns
  • 2 Code node execution modes

Files

SKILL.mdMarkdownGitHub ↗

JavaScript Code Node

Expert guidance for writing JavaScript code in n8n Code nodes.

---

Quick Start

// 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)
// 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)
// 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

// 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

// 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

// 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

// 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 for comprehensive guide

---

Critical: Webhook Data Structure

MOST COMMON MISTAKE: Webhook data is nested under .body

// ❌ 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 for full webhook structure details

---

Return Format Requirements

CRITICAL RULE: Always return array of objects with json property

Correct Return Formats

// ✅ 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

// ❌ 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 #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

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

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

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

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

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 for 10 detailed production patterns

---

Error Prevention - Top 5 Mistakes

#1: Empty Code or Missing Return (Most Common)

// ❌ 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

// ❌ 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

// ❌ WRONG: Returning object instead of array
return {json: {result: 'success'}};

// ✅ CORRECT: Array wrapper required
return [{json: {result: 'success'}}];

#4: Missing Null Checks

// ❌ 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

// ❌ WRONG: Direct access to webhook data
const email = $json.email;

// ✅ CORRECT: Webhook data under .body
const email = $json.body.email;

See: ERROR_PATTERNS.md for comprehensive error guide

---

Built-in Functions & Helpers

$helpers.httpRequest()

Make HTTP requests from within code:

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:

// 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:

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 for complete reference

---

Best Practices

1. Always Validate Input Data

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

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

// ✅ 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

// ✅ 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

// ✅ 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()

// 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 - Comprehensive data access patterns
  • COMMON_PATTERNS.md - 10 production-tested patterns
  • ERROR_PATTERNS.md - Top 5 errors and solutions
  • 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.

Related skills

vercel-labsAgent BrowserGive their coding agent reliable, high-fidelity control over any website or Electron desktop app.591k39.6kopen.feishu.cnLark ApprovalLet their AI coding agent create, read, update, and approve items in Lark (Feishu) approval workflows without leaving the coding environment.494kopen.feishu.cnLark EventHandle Feishu/Lark bot events, webhooks, and subscription callbacks in agent-driven backend code.493kopen.feishu.cnLark Workflow Meeting SummaryAutomatically generate structured meeting summaries and action items from Lark/Feishu calls without manual note-taking.492kopen.feishu.cnLark Workflow Standup ReportAutomatically generate and post daily standup reports in Lark/Feishu from their workflow and activity data.492k101-skillsTwitter AutomationAutomate X/Twitter posts, scheduling, and engagement via X API integration441k669

FAQ

Why is my webhook data undefined in an n8n Code node?

Webhook data is nested under the .body property, so read $json.body.name rather than $json.name.

What must a Code node return?

An array of objects each with a json property, for example [{json: {...}}].

Automation & Workflowsworkflow
Browse by category
AI & AgentsFrontend & DesignBackend & DataDev ToolsAutomationTesting & ReviewSecurityMonitoring & CloudDocs & Planning
Design & frontend
Design systemsAnimation & motionAccessibility (a11y)CSS & TailwindUI designUXDesign to codeshadcn/uiLanding pagesBest design skills
Most searched skills
find-skillscavemanfrontend-designbrainstormingsystematic-debuggingstop-slopemil-design-engui-ux-pro-maxkarpathy-guidelinesweb-design-guidelinesreact-best-practicesgrill-meimprovemicrosoft-foundryagent-browser
Browse all listings
All agent skillsAll MCP serversAll marketplacesAll plugins

This week in AI coding

Five minutes, every Monday - the tools, releases and tactics for developers.

unsubscribe anytime.