Understanding package.json and Writing Custom JSON Scripts in Node.js

NodeJs

"Node.js is like a magical kitchen for JavaScript—originally, it could only cook in the browser, but now it can build backends, manage servers, and even make coffee... if there's an npm package for it!"

 

Do you know what makes every Node.js project tick?

That’s right – package.json!

This little file is the heart and soul of any Node.js project. It stores:

• Project details (name, version, author, description)
• Dependencies (npm packages)
• Scripts (custom commands)
• Configuration settings

In this fun guide, you’ll learn:

• What is package.json?
• How to create and modify it?
• How to write and run custom scripts?

Let’s dive in!

1️What is package.json?

Think of package.json as a Node.js project’s ID card.

It tells npm everything about your project:

• The name, version, and description
• The dependencies it needs
• Custom scripts to automate tasks

Example of a package.json file

{
  "name": "my-awesome-app",
  "version": "1.0.0",
  "description": "An amazing app built with Node.js",
  "main": "index.js",
  "scripts": {
    "start": "node index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "John Doe",
  "license": "MIT",
  "dependencies": {
    "express": "^4.18.2"
  }
}

2️Creating package.json

Option 1: Using npm init (Manual Mode)

Run this in your terminal:

npm init

You’ll be asked a series of questions (name, version, description, entry file, etc.).

At the end, it will generate a complete package.json file for you!

Option 2: Using npm init -y (Automatic Mode)

If you’re in a hurry , just use:

npm init -y

This creates package.json with default values:

{
  "name": "my-project",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {},
  "author": "",
  "license": "ISC"
}

3️ Understanding Key Sections of package.json

1. name and version

• name: Project name (must be unique if publishing to npm).
• version: Follows Semantic Versioning (major.minor.patch).

Example:

"name": "super-app",
"version": "2.1.0"

2. dependencies and devDependencies

• dependencies: Packages needed for production.
• devDependencies: Packages needed only during development (e.g., testing tools).

Adding a Dependency

npm install express

Updates package.json:

"dependencies": {
  "express": "^4.18.2"
}

Adding a Dev Dependency

npm install nodemon --save-dev

Updates package.json:

"devDependencies": {
  "nodemon": "^2.0.22"
}

3. scripts (Custom Commands in Node.js)

Scripts let you automate tasks like running the app, testing, or deploying.

Example:

"scripts": {
  "start": "node index.js",
  "dev": "nodemon index.js",
  "test": "jest"
}

Running a Script:

npm run dev

4️Writing Custom npm Scripts

Want to be lazy but productive? Automate tasks with custom npm scripts!

Example 1: Run a Server with a Single Command

Add this inside "scripts":

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

Run it with:

npm start

Example 2: Delete node_modules and Reinstall Dependencies

Add this custom script:

"scripts": {
  "refresh": "rm -rf node_modules package-lock.json && npm install"
}

Run it with:

npm run refresh

Example 3: Print a Funny Message

Let’s add a fun custom script:

"scripts": {
  "joke": "echo 'Why did the programmer quit his job? Because he didn’t get arrays. '"
}

Run it:

npm run joke

Output:

Why did the programmer quit his job? Because he didn’t get arrays. 

Fun fact: npm scripts can run shell commands!

Example 4: Open a Website in Your Browser

Want to open Google with a command? Try this:

"scripts": {
  "open": "start https://www.google.com"
}

Run it:

npm run open

Note:

• On Mac/Linux, replace start with open.
• On Windows, start works fine.

5️Running Multiple Scripts at Once

Let’s say you want to:

1. Run a server
2. Watch for file changes

Use & to run them together:

"scripts": {
  "dev": "nodemon server.js & node anotherTask.js"
}

Or, for cross-platform support, use npm-run-all:

npm install npm-run-all --save-dev

Modify package.json:

"scripts": {
  "dev": "npm-run-all --parallel watch start"
}

Now run:

npm run dev

Perfect for full-stack apps!

 

Conclusion

Now you’re a package.json ninja!

• You understand what package.json does.
• You can install dependencies and devDependencies.
• You can write and run custom npm scripts.

Next step? Automate your workflow like a pro!

Happy coding!