How to Use Nodemon in Node.js for Automatic Server Restart

Use nodemon to automatically restart your Node.js app when files change by installing it with npm install -g nodemon and running your app with nodemon your-app.js. This saves time by avoiding manual restarts during development.

Syntax

The basic syntax to run your Node.js app with nodemon is:

• nodemon <script>: Starts nodemon to watch your script file and restart on changes.
• nodemon --watch <folder>: Watches a specific folder for changes.
• nodemon --ext <extensions>: Watches files with specific extensions.

bash

nodemon app.js
nodemon --watch src --ext js,json app.js

Example

This example shows how to run a simple Node.js server with nodemon. When you save changes to server.js, nodemon restarts the server automatically.

javascript

const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello from nodemon!');
});

server.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

Output

Server running on http://localhost:3000

Common Pitfalls

Common mistakes when using nodemon include:

• Not installing nodemon globally or locally before use.
• Running node app.js instead of nodemon app.js, which disables auto-restart.
• Not saving files after changes, so nodemon does not detect updates.
• Ignoring configuration files like nodemon.json for complex setups.

bash

/* Wrong way - nodemon not used */
node server.js

/* Right way - use nodemon */
nodemon server.js

Quick Reference

Command	Description
nodemon app.js	Start app with nodemon watching all files
nodemon --watch src app.js	Watch only the src folder
nodemon --ext js,json app.js	Watch only .js and .json files
nodemon --delay 2 app.js	Wait 2 seconds before restarting
nodemon --exec "npm run start" app.js	Run custom command on restart

Key Takeaways

Install nodemon globally with npm to use it anywhere.

Run your app with nodemon instead of node to auto-restart on changes.

Use --watch and --ext options to control which files nodemon watches.

Save your files to trigger nodemon restarts.

Use nodemon.json for advanced configuration.