Code Node

The Code node executes custom JavaScript or Python code inside a workflow. Use it for data transformation, complex logic, API calls, and anything that built-in nodes cannot handle directly.

Language Modes

Mode	Runtime	Notes
JavaScript	Node.js (V8)	Default mode. Full access to n8n helper APIs.
Python	Python 3 (via Pyodide)	Available in n8n 1.0+. Some limitations on external libraries.

Run Modes

Mode	Behavior
Run Once for All Items	The code receives all input items at once as an array. Use this when you need to aggregate, sort, or compare across items.
Run Once for Each Item	The code runs separately for every input item. Use this for simple per-item transformations.

Warning: Run mode affects which APIs are available

In Run Once for All Items mode, use $input.all() to get all items. In Run Once for Each Item mode, use $input.item to get the current item. Mixing these up is the most common source of Code node errors.

Available APIs (JavaScript)

API	Description
$input.all()	Returns all input items as an array. Each item has .json and optional .binary properties. Available in "All Items" mode.
$input.item	Returns the current input item. Available in "Each Item" mode.
$input.first()	Returns the first input item.
$input.last()	Returns the last input item.
$json	Shorthand for $input.item.json in "Each Item" mode. Gives direct access to the current item's data.
$('Node Name').all()	Access output items from any upstream node by name.
$('Node Name').first()	Access the first output item from a named upstream node.
$execution.id	The current execution ID.
$workflow.id	The current workflow ID.
$workflow.name	The current workflow name.
$env	Access environment variables defined on the n8n instance (e.g., $env.API_KEY).
$now	Current timestamp as a Luxon DateTime object.
$today	Today's date at midnight as a Luxon DateTime object.
this.helpers.httpRequest()	Make HTTP requests from within the Code node. Supports the same options as the HTTP Request node.

Built-in Libraries

These libraries are available without any require() or import statements:

Library	Access	Use Case
Luxon	const { DateTime } = require('luxon')	Date and time parsing, formatting, math, and timezone conversion.
JMESPath	const jmespath = require('jmespath')	Query and extract data from complex JSON structures.
Lodash	const _ = require('lodash')	Utility functions for arrays, objects, and strings. Available in most n8n versions.

Note

External npm modules are not available by default. Self-hosted users can allow specific modules via the NODE_FUNCTION_ALLOW_EXTERNAL environment variable (e.g., NODE_FUNCTION_ALLOW_EXTERNAL=axios,moment). n8n Cloud does not support external modules.

Return Format

The Code node must return an array of items. Each item is an object with a json property:

// Run Once for All Items
const items = $input.all();
const results = [];

for (const item of items) {
  results.push({
    json: {
      name: item.json.name.toUpperCase(),
      processed: true,
    },
  });
}

return results;

// Run Once for Each Item
return {
  json: {
    name: $json.name.toUpperCase(),
    processed: true,
  },
};

Warning: Always return { json: {...} }

If you return plain objects without the json wrapper, downstream nodes will receive empty items. This is the second most common Code node mistake.

Common Patterns

Transform and reshape data (All Items):

const items = $input.all();
return items.map(item => ({
  json: {
    fullName: `${item.json.firstName} ${item.json.lastName}`,
    email: item.json.email.toLowerCase(),
    createdAt: DateTime.fromISO(item.json.date).toFormat('yyyy-MM-dd'),
  },
}));

Filter items by a condition:

const items = $input.all();
return items.filter(item => item.json.status === 'active');

Aggregate data across items:

const items = $input.all();
const total = items.reduce((sum, item) => sum + item.json.amount, 0);

return [{ json: { total, count: items.length, average: total / items.length } }];

Make an HTTP request inside the Code node:

const response = await this.helpers.httpRequest({
  method: 'GET',
  url: 'https://api.example.com/data',
  headers: { Authorization: 'Bearer ' + $env.API_TOKEN },
});

return [{ json: response }];

Access data from a previous node by name:

const webhookData = $('Webhook').first().json;
const dbRows = $('PostgreSQL').all();

return dbRows.map(row => ({
  json: {
    ...row.json,
    triggeredBy: webhookData.headers.host,
  },
}));

Tips and Gotchas

Warning: Async/await is required for HTTP calls

When using this.helpers.httpRequest() or any promise-based API, you must use await. Without it, the node returns a Promise object instead of the actual data.

• $input.all() vs $input.item. In "All Items" mode, $input.item is undefined. In "Each Item" mode, $input.all() works but is inefficient because it fetches all items on every iteration.
• Returning nothing stops the workflow. If your code returns an empty array [], downstream nodes will not execute. Return at least one item or use a conditional branch.
• console.log() output. Logs appear in the n8n server console (Docker logs, terminal output). They do not appear in the editor UI. Use them for debugging on self-hosted instances.
• Error handling. Wrap risky code in try/catch. Unhandled exceptions stop the workflow. Use this.continueOnFail() to check if the node is configured to continue on failure.
• Python mode limitations. Python mode does not have access to this.helpers or the same helper functions. Use the _input and _execution objects instead. External Python packages are limited to what Pyodide bundles.
• Large data sets. Processing tens of thousands of items in a single Code node can consume significant memory. For very large data, consider streaming with the HTTP Request node or processing in batches using a Loop node.

Common Errors

TypeError: Cannot read properties of undefined (reading 'json') You are using $input.item in "Run Once for All Items" mode, where it is undefined. Switch to $input.all() to get the array of items, or change the run mode to "Run Once for Each Item."

Error: The output of the code node must be an array of objects with a "json" property. Your code is returning plain objects instead of wrapping them in { json: {...} }. Every returned item must have a json key. For example, return [{ json: { name: "Alice" } }] instead of [{ name: "Alice" }].

ReferenceError: require is not defined (when trying to load external modules) External npm modules are not available by default. On self-hosted instances, allow specific modules via the NODE_FUNCTION_ALLOW_EXTERNAL environment variable (e.g., NODE_FUNCTION_ALLOW_EXTERNAL=axios,moment). On n8n Cloud, external modules are not supported -- use the built-in libraries (Luxon, Lodash, JMESPath) or this.helpers.httpRequest() instead.

See Also

• Code Node Mastery Tips
• Expressions & Variables
• Data Transformation Tips