How to add a custom code node on n8n

Open terminal and run git clone https://github.com/n8n-io/n8n-nodes-starter then cd n8n-nodes-starter. This provides boilerplate package.json, tsconfig.json, and node examples for quick setup.

Run npm install to fetch TypeScript, n8n-workflow, and dev dependencies. Edit package.json to set "name": "n8n-nodes-mycustom" (prefix with n8n-nodes-), version, and scripts like "build": "tsc" and "dev": "tsc --watch".

import { IExecuteFunctions } from 'n8n-core';
import { INodeType, INodeTypeDescription } from 'n8n-workflow';

export class MyCustomNode implements INodeType {
  description: INodeTypeDescription = {
    displayName: 'My Custom Node',
    name: 'myCustomNode',
    group: ['transform'],
    version: 1,
    description: 'Reverses input string',
    defaults: { name: 'My Custom Node', color: '#1F8EB2' },
    inputs: ['main'],
    outputs: ['main'],
    properties: [{
      displayName: 'String to Reverse',
      name: 'stringToReverse',
      type: 'string',
      default: '',
      placeholder: 'Enter string'
    }]
  };

  async execute(this: IExecuteFunctions) {
    const items = this.getInputData();
    const returnData = [];
    const stringToReverse = this.getNodeParameter('stringToReverse', 0) as string;
    returnData.push({ json: { reversed: stringToReverse.split('').reverse().join('') } });
    return this.prepareOutputData(returnData);
  }
}

Save as nodes/MyCustomNode/MyCustomNode.node.ts. Update index.ts to export the class.

Ensure tsconfig.json has "outDir": "./dist", "target": "ES2019", "module": "CommonJS", and includes your node files. This compiles TS to JS in /dist/.

Run npm run build to compile TypeScript to JavaScript in the dist/ folder. Verify dist/node/ and dist/credentials/ (if any) contain your files.

Create ~/.n8n/custom/ if missing. Copy dist/node/ and dist/credentials/ into it, then cd ~/.n8n/custom/, run npm init -y, and npm install.

Restart your n8n instance (e.g., docker restart n8n or kill/restart local process). Open n8n at http://localhost:5678, create a new workflow, click +, and search for 'My Custom Node'.

FROM n8nio/n8n:latest
USER root
COPY ./dist /home/node/.n8n/custom/
USER node

Build custom image with your docker-compose.yml mounting ./dist:/home/node/.n8n/custom/node_modules/n8n-nodes-mycustom. Match n8n version.

Add the node to a workflow, input a string, execute, and verify output (e.g., 'hello' becomes 'olleh'). Check logs with docker logs n8n for module resolution issues.

Add descriptions, icons (SVG in node folder), and properties to description object. Modularize with helpers and constants for complex logic.