Setup Nodemon to auto restart Nodejs application server

September 10, 2017

Manually restarting Node.js application is a tiring and tedious job. Nodemon is the best solution available to autorestart a nodejs app server in development mode.

First step

Organize the source directory src and initiate it with an app.js or index.js or server.js or any other convention you use to bootstrap a Node.js server.

Update the package.json file accordingly by adding a start script.

code

{
  "name": "nodemon-auto-restart",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "node src/index.js"
  },
  "keywords": [],
  "author": "Aland Baban <Aland Baban> (http://Aland Baban/)",
  "license": "MIT"
}

Second step

Add express or any other framework as dependency to bootstrap a minimal server.

Code for a minimal server:

code

'use strict';

const express = require('express');
const app = express();

app.use('/', (req, res) => {
  res.status(200).send('Hello World!');
});

app.listen(3000);

In first terminal window start the server:

code

$ npm run start
> node src/index.js

In second terminal window, request the url to test if the api is working and to see the response message:

code

$ curl -X GET http://localhost:3000/
Hello World!

Now if I change the response message, I have to restart the server to get the desired result:

code

app.use('/', (req, res) => {
  res.status(200).send('Lorem Ipsum');
});

Use Ctrl + C to stop the currently running server and restart it by using the same command before: npm run start.

Using the curl command again from terminal window we get the desired result:

code

curl -X GET http://localhost:3000/
Lorem Ipsum

This whole process is repetitive will slow your development of any package or application. Better solution is to use nodemon.

Third step

Add nodemon as devDependency:

code

$ npm i -D nodemon

code

{
  "name": "nodemon-auto-restart",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "node src/index.js"
  },
  "keywords": [],
  "author": "Aland Baban <Aland Baban> (http://Aland Baban/)",
  "license": "MIT",
  "dependencies": {
    "express": "4.15.3"
  },
  "devDependencies": {
    "nodemon": "1.11.0"
  }
}

Fourth step

Make another script dev under npm scripts in package.json file:

code

{
  "scripts": {
    "start": "node src/index.js",
    "dev": "nodemon --watch src src/index.js"
  }
}

Now run $ npm run dev and request using curl command, we will see the last familiar result:

code

curl -X GET http://localhost:3000/
Lorem Ipsum

If I change the response message in index.js file back to Hello World, this time I don't I have to restart the server since nodemon is watching for the changes using inside the src directory, through its --watchparameter. If I use the curl command again, the result is familiar with the update:

code

curl -X GET http://localhost:3000/
Hello World

One can verify by observing the log messages in the terminal window where nodemon is running:

code

$ npm run dev

> nodemon-auto-restart@1.0.0 dev /Users/alandbaban/github/nodemon-auto-restart
> nodemon --watch src src/index.js

[nodemon] 1.11.0
[nodemon] to restart at any time, enter `rs`
[nodemon] watching: /Users/alandbaban/github/nodemon-auto-restart/src/**/*
[nodemon] starting `node src/index.js`
[nodemon] restarting due to changes...
[nodemon] starting `node src/index.js`

To stop the nodemon process, use Ctrl + C.

Full Source at this Github Repository.

Originally Published at Hackernoon.com