How to Change npm start Script of Node.js ? - GeeksforGeeks (2024)

In Node.js, npm (Node Package Manager) provides a convenient way to manage project scripts through the scripts field in the package.json file. By default, the npm start command is used to start your Node.js application. However, you might need to customize this command to suit specific requirements, such as running a different entry point, adding environment variables, or incorporating additional setup steps. This article will guide you through the process of changing the npm start script in a Node.js application.

What is npm start?

The npm start command is a predefined script that runs when you execute npm start in your terminal. It is a shorthand for npm run start, which invokes the start script defined in your package.json file. If no start script is defined, npm will attempt to run node server.js by default.

Default npm start Behaviour

{
 "scripts": {
 "start": "node server.js"
 }
}

In this example, running npm start will execute node server.js.

Why Customize the npm start Script?

Customizing the npm start script can be useful for various reasons:

• Changing the Entry Point: You might want to start your application using a different file or set of files.
• Environment Configuration: You might need to set specific environment variables or configurations before starting the application.
• Additional Tasks: You might want to perform tasks like compiling TypeScript, setting up a database connection, or launching auxiliary services before starting the main application.

Example: Implementation to build a server on node.js

// Importing http moduleconst http = require("http")// Creating Serverconst server = http.createServer((req,res)=>{ req.statusCode=200; console.log("Server is Started") res.end();});// Executing the serverserver.listen(3000,"localhost",()=>{ console.log("Server is Running ")})

Step to Run Application:Run the application using the following command from the root directory of the project

node index.js

Output:

When no execution file mentioned in the npm start script npm automatically runs the node server.js file if available in the project directory.

package.json

Example: Implementation to build a server on node.js

// server.js// Importing http moduleconst http = require("http")// Creating Serverconst server = http.createServer((req,res)=>{ req.statusCode=200; console.log("Server is Executed") res.end();});// Executing the serverserver.listen(3000,"localhost",()=>{ console.log("This is server.js file")})

Step to Run Application:Run the application using the following command from the root directory of the project

node server.js

Output:

Using nodemon for Automatic Restart

For development purposes, you can use nodemon to automatically restart your application when file changes are detected.

npm install nodemon --save-dev

Update the start script to use nodemon:

{
 "scripts": {
 "start": "nodemon app.js"
 }
}

Conclusion

Customizing the npm start script in a Node.js application allows you to tailor the startup process to meet specific requirements. Whether you need to change the entry point, set environment variables, run additional tasks, or use a process manager, modifying the start script is a flexible and straightforward way to enhance your project’s startup procedure. By understanding and utilizing the various options available, you can improve the efficiency and maintainability of your Node.js applications.