# N8n Code Javascript > Write JavaScript code in n8n Code nodes. Use when writing custom JavaScript, accessing data in Code nodes, transforming data programmatically, handling multiple items, or debugging Code node errors. Use when this capability is needed. - Skill: `tomevault-io/n8n-code-javascript` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/n8n-code-javascript` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/n8n-code-javascript/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/n8n-code-javascript --- # n8n Code JavaScript Expert guidance for writing JavaScript in n8n Code nodes. > Based on [n8n-skills](https://github.com/czlonkowski/n8n-skills) by Romuald Członkowski ## Code Node Modes ### Run Once for All Items Process all items together. **Most common mode**. ```javascript // Access all input items const items = $input.all(); // Process and return return items.map(item => ({ json: { ...item.json, processed: true } })); ``` ### Run Once for Each Item Process each item separately. ```javascript // Access current item const data = $input.item.json; // Return single item return { json: { ...data, processed: true } }; ``` ## Accessing Data ### Current Node Input ```javascript // All items const items = $input.all(); // First item const first = $input.first(); // Current item (in "each item" mode) const current = $input.item; // JSON data const data = $input.first().json; ``` ### Previous Nodes ```javascript // From specific node const nodeData = $node["Node Name"].all(); const firstItem = $node["HTTP Request"].first().json; // From input (same as previous node) const inputItems = $input.all(); ``` ### Execution Context ```javascript // Workflow info const workflowId = $workflow.id; const workflowName = $workflow.name; // Execution info const executionId = $execution.id; // Environment variables const apiKey = $env.API_KEY; // n8n variables const myVar = $vars.myVariable; ``` ## Common Patterns ### Transform All Items ```javascript const items = $input.all(); return items.map(item => ({ json: { id: item.json.id, name: item.json.name.toUpperCase(), createdAt: new Date().toISOString() } })); ``` ### Filter Items ```javascript const items = $input.all(); return items.filter(item => item.json.status === 'active'); ``` ### Aggregate Data ```javascript const items = $input.all(); const total = items.reduce((sum, item) => sum + item.json.amount, 0); const count = items.length; return [{ json: { total, count, average: total / count } }]; ``` ### Group By ```javascript const items = $input.all(); const grouped = {}; for (const item of items) { const key = item.json.category; if (!grouped[key]) grouped[key] = []; grouped[key].push(item.json); } return Object.entries(grouped).map(([category, items]) => ({ json: { category, items, count: items.length } })); ``` ### Fetch External Data ```javascript const response = await fetch('https://api.example.com/data', { headers: { 'Authorization': `Bearer ${$env.API_TOKEN}` } }); const data = await response.json(); return [{ json: data }]; ``` ### Error Handling ```javascript const items = $input.all(); return items.map(item => { try { const parsed = JSON.parse(item.json.rawData); return { json: { success: true, data: parsed } }; } catch (error) { return { json: { success: false, error: error.message } }; } }); ``` ## Webhook Data Access **CRITICAL**: In Code nodes, webhook data is under `.body`: ```javascript // ❌ Wrong const message = $input.first().json.message; // ✅ Correct - webhook data is in body const message = $input.first().json.body.message; const headers = $input.first().json.headers; const query = $input.first().json.query; ``` ## Date/Time with Luxon n8n includes [Luxon](https://moment.github.io/luxon/) for dates: ```javascript const { DateTime } = require('luxon'); // Current time const now = DateTime.now(); // Parse date const date = DateTime.fromISO('2024-01-15'); // Format const formatted = now.toFormat('yyyy-MM-dd HH:mm:ss'); // Add/subtract const nextWeek = now.plus({ days: 7 }); const yesterday = now.minus({ days: 1 }); // Compare const isAfter = now > date; const diff = now.diff(date, 'days').days; ``` ## Binary Data ### Access Binary ```javascript const items = $input.all(); for (const item of items) { if (item.binary?.data) { const buffer = await item.binary.data.toBuffer(); const base64 = buffer.toString('base64'); // Process binary... } } ``` ### Create Binary ```javascript const data = { key: 'value' }; const jsonString = JSON.stringify(data, null, 2); const buffer = Buffer.from(jsonString); return [{ json: { fileName: 'data.json' }, binary: { data: await this.helpers.prepareBinaryData(buffer, 'data.json', 'application/json') } }]; ``` ## Common Mistakes ### 1. Wrong Return Format ```javascript // ❌ Wrong - must return array of objects with json property return { name: 'John' }; // ✅ Correct return [{ json: { name: 'John' } }]; ``` ### 2. Not Returning All Items ```javascript // ❌ Wrong - returns only first item const item = $input.first(); return [{ json: item.json }]; // ✅ Correct - process all items return $input.all().map(item => ({ json: item.json })); ``` ### 3. Accessing Wrong Data Level ```javascript // ❌ Wrong - items don't have .data const data = items[0].data; // ✅ Correct - use .json const data = items[0].json; ``` ### 4. Missing await for Async ```javascript // ❌ Wrong - fetch is async const response = fetch(url); // ✅ Correct const response = await fetch(url); const data = await response.json(); ``` ## Available Libraries Built-in libraries available in Code node: - `luxon` - Date/time handling - `lodash` - Utility functions - `crypto` - Cryptographic functions ```javascript const { DateTime } = require('luxon'); const _ = require('lodash'); const crypto = require('crypto'); // Use lodash const grouped = _.groupBy(items, 'category'); // Use crypto const hash = crypto.createHash('sha256').update(data).digest('hex'); ``` ## Best Practices 1. **Always return array** of `{ json: {...} }` objects 2. **Use `try/catch`** for error-prone operations 3. **Access webhook data** via `.body` 4. **Use Luxon** for dates, not raw Date() 5. **Validate input data** before processing 6. **Log sparingly** - console.log works but adds overhead ## Quick Reference | Need | Code | |------|------| | All items | `$input.all()` | | First item | `$input.first()` | | Current item | `$input.item` (each mode) | | Item JSON | `item.json` | | Webhook body | `item.json.body` | | Other node | `$node["Name"].first().json` | | Env var | `$env.VAR_NAME` | | Return item | `{ json: {...} }` | | Return many | `[{ json: {...} }, ...]` | --- Based on [n8n-skills](https://github.com/czlonkowski/n8n-skills) by Romuald Członkowski • Adapted for Moltbot by fazer.ai --- > Source: [fazer-ai/moltbot-skill-n8n](https://github.com/fazer-ai/moltbot-skill-n8n) — distributed by [TomeVault](https://tomevault.io).