Node.js package.json Practice Questions with Solutions

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Introduction

package.json is one of the most important files in a Node.js project. It stores project information, scripts, dependencies, development dependencies, version details, and other configuration settings. In this chapter, you will practice creating and editing package.json, adding scripts, managing dependencies, understanding versions, setting the main file, adding project information, and working with common package.json properties through simple step-by-step examples. Node.js package.json practice questions with solutions help to understand the concepts.

Question 1: How do you create a package.json file?

Problem

Create a new Node.js project and generate a package.json file using npm.

Solution

Create a project folder:

mkdir package-json-practice

Move into the folder:

cd package-json-practice

Now run:

npm init

npm will ask you several questions.

You can also use:

npm init -y

This creates the file using default values.

Output

A new file will be created:

package-json-practice/
└── package.json

Example package.json

{
    "name": "package-json-practice",
    "version": "1.0.0",
    "description": "",
    "main": "index.js",
    "scripts": {
        "test": "echo \"Error: no test specified\" && exit 1"
    },
    "keywords": [],
    "author": "",
    "license": "ISC"
}

Step-by-Step Explanation

  1. Create a project folder.
  2. Open the folder in the terminal.
  3. Run npm init.
  4. npm asks for project information.
  5. npm creates package.json.
  6. package.json becomes the main configuration file for your npm project.

Question 2: How do you change the name and version in package.json?

Problem

Create a project named student-app with version 1.0.0.

Solution

Run:

npm init -y

Then open package.json and update it:

{
    "name": "student-app",
    "version": "1.0.0",
    "description": "A simple Node.js student application",
    "main": "index.js",
    "scripts": {},
    "keywords": [
        "nodejs",
        "student"
    ],
    "author": "Student",
    "license": "ISC"
}

Output

Your project information is now stored inside package.json.

Step-by-Step Explanation

The name property stores the project name:

"name": "student-app"

The version property stores the project version:

"version": "1.0.0"

The version usually follows:

MAJOR.MINOR.PATCH

For example:

1.0.0

Version Example

A bug fix might increase:

1.0.0 → 1.0.1

A new backward-compatible feature might increase:

1.0.1 → 1.1.0

A major breaking change might increase:

1.1.0 → 2.0.0

Question 3: How do you add a description and keywords to package.json?

Problem

Create a package.json file for a Node.js learning project and add a description and keywords.

Solution

{
    "name": "node-learning",
    "version": "1.0.0",
    "description": "A beginner-friendly Node.js learning project",
    "main": "index.js",
    "keywords": [
        "nodejs",
        "javascript",
        "backend",
        "programming"
    ],
    "author": "Student",
    "license": "ISC"
}

Output

The project now contains useful information about itself.

Step-by-Step Explanation

The description property explains what the project does:

"description": "A beginner-friendly Node.js learning project"

The keywords property contains words related to the project:

"keywords": [
    "nodejs",
    "javascript",
    "backend"
]

Keywords are stored as an array.

Question 4: What is the main property in package.json?

Problem

Create a Node.js project where index.js is the main application file.

Solution

Create index.js:

console.log("Node.js application started.");

Then configure package.json:

{
    "name": "my-node-app",
    "version": "1.0.0",
    "main": "index.js"
}

Output

The project structure:

my-node-app/
├── index.js
└── package.json

Step-by-Step Explanation

The main property identifies the primary entry file of the package:

"main": "index.js"

If your main file is named app.js, you can write:

"main": "app.js"

Question 5: How do you add npm scripts in package.json?

Problem

Create start and dev scripts for a Node.js application.

Solution

First install Nodemon as a development dependency:

npm install --save-dev nodemon

Now add scripts:

{
    "name": "my-node-app",
    "version": "1.0.0",
    "main": "index.js",
    "scripts": {
        "start": "node index.js",
        "dev": "nodemon index.js"
    },
    "devDependencies": {
        "nodemon": "^3.0.0"
    }
}

The exact Nodemon version may differ on your system.

Run the Start Script

npm start

This executes:

node index.js

Run the Development Script

npm run dev

This executes:

nodemon index.js

Step-by-Step Explanation

  1. Create the scripts object.
  2. Add the start script.
  3. Add the dev script.
  4. npm start runs the start script.
  5. npm run dev runs the dev script.

Question 6: How do dependencies appear in package.json?

Problem

Install Express and understand how npm records it inside package.json.

Solution

Initialize the project:

npm init -y

Install Express:

npm install express

npm automatically adds Express to dependencies.

Your package.json will contain something similar to:

{
    "name": "my-node-app",
    "version": "1.0.0",
    "dependencies": {
        "express": "^5.0.0"
    }
}

The exact version may be different when you install it.

Step-by-Step Explanation

  1. Run npm init -y.
  2. npm creates package.json.
  3. Run npm install express.
  4. npm downloads Express.
  5. npm adds Express to dependencies.
  6. npm also updates package-lock.json.

Question 7: How do you add a development dependency to package.json?

Problem

Install Nodemon as a development dependency and understand where it appears in package.json.

Solution

Run:

npm install --save-dev nodemon

Your package.json will contain something similar to:

{
    "name": "my-node-app",
    "version": "1.0.0",
    "scripts": {
        "dev": "nodemon index.js"
    },
    "devDependencies": {
        "nodemon": "^3.0.0"
    }
}

Step-by-Step Explanation

  1. --save-dev tells npm that the package is for development.
  2. npm installs Nodemon.
  3. npm adds it to devDependencies.
  4. You can use Nodemon through an npm script.

Dependencies

"dependencies": {
    "express": "^5.0.0"
}

Development Dependencies

"devDependencies": {
    "nodemon": "^3.0.0"
}

Question 8: How do you use type: module in package.json?

Problem

Configure a Node.js project to use ES Modules and allow import and export.

Solution

Add:

{
    "name": "es-module-practice",
    "version": "1.0.0",
    "type": "module"
}

Create math.js:

export function add(a, b) {
    return a + b;
}

Create index.js:

import { add } from "./math.js";

const result = add(10, 20);

console.log(result);

Run:

node index.js

Output

30

Step-by-Step Explanation

Normally, Node.js projects can use CommonJS syntax such as:

const fs = require("fs");

When you set:

"type": "module"

you can use ES Module syntax:

import fs from "fs";

and:

export function add() {
}

Important Point

When using ES Modules with local files, include the file extension:

import { add } from "./math.js";

Question 9: How do you remove a dependency from package.json?

Problem

Install Lodash and then remove it from your project.

Solution

Install Lodash:

npm install lodash

Now remove it:

npm uninstall lodash

Before

Your package.json may contain:

{
    "dependencies": {
        "lodash": "^4.17.21"
    }
}

After

The Lodash dependency is removed:

{
    "dependencies": {}
}

Depending on the other packages in your project, the dependencies section may contain other packages or may disappear from the file.

Step-by-Step Explanation

  1. Install the package.
  2. npm adds it to dependencies.
  3. Run npm uninstall lodash.
  4. npm removes the package from node_modules.
  5. npm removes its entry from package.json.
  6. npm updates package-lock.json.

General Command

npm uninstall package-name

For example:

npm uninstall express

Question 10: How do you create a complete package.json for a Node.js project?

Problem

Create a complete Node.js project configuration containing:

  • Project information
  • Main file
  • npm scripts
  • Dependencies
  • Development dependencies
  • ES Module configuration

Solution

Create a project:

mkdir complete-node-project

Move into it:

cd complete-node-project

Initialize npm:

npm init -y

Install Express:

npm install express

Install Nodemon:

npm install --save-dev nodemon

Now create index.js:

import express from "express";

const app = express();

const PORT = 3000;

app.get("/", (req, res) => {
    res.send("Welcome to my Node.js project!");
});

app.get("/about", (req, res) => {
    res.send("This is the About page.");
});

app.listen(PORT, () => {
    console.log(
        `Server running at http://localhost:${PORT}`
    );
});

Now configure package.json:

{
    "name": "complete-node-project",
    "version": "1.0.0",
    "description": "A beginner Node.js project using Express",
    "main": "index.js",
    "type": "module",
    "scripts": {
        "start": "node index.js",
        "dev": "nodemon index.js"
    },
    "keywords": [
        "nodejs",
        "express",
        "javascript",
        "backend"
    ],
    "author": "Student",
    "license": "ISC",
    "dependencies": {
        "express": "^5.0.0"
    },
    "devDependencies": {
        "nodemon": "^3.0.0"
    }
}

The exact Express and Nodemon versions may be different when you install them.

Run the Application

For normal execution:

npm start

For development:

npm run dev

Output

Terminal:

Server running at http://localhost:3000

Open:

http://localhost:3000/

Browser:

Welcome to my Node.js project!

Open:

http://localhost:3000/about

Browser:

This is the About page.

Step-by-Step Explanation

  1. Create the project folder.
  2. Run npm init -y.
  3. npm creates package.json.
  4. Install Express.
  5. Install Nodemon as a development dependency.
  6. Add "type": "module" to use import.
  7. Set index.js as the main file.
  8. Add start and dev scripts.
  9. Add project information.
  10. Start the application using npm start.
  11. Use npm run dev during development.
  12. npm keeps the project’s package information and dependencies inside package.json.

Key Takeaways

  • package.json is a central configuration file for Node.js npm projects.
  • npm init creates a package.json file.
  • npm init -y creates one using default values.
  • The name property stores the project name.
  • The version property stores the project version.
  • The description property explains the project.
  • The main property identifies the package’s main entry file.
  • The scripts property stores commands that can be run with npm.
  • npm start runs the start script.
  • Custom scripts can be run with npm run script-name.
  • dependencies contains packages needed by the application.
  • devDependencies contains packages mainly used during development.
  • keywords stores words related to the project.
  • author stores author information.
  • license specifies the project’s license.
  • "type": "module" enables ES Module behavior for .js files in that package scope.
  • Installing packages with npm automatically updates package.json.
  • Uninstalling a package removes its dependency entry.
  • package-lock.json records the resolved dependency tree and versions.
  • package.json makes it easier for other developers and deployment systems to understand and install a Node.js project.

FAQs

1. What is package.json in Node.js?

package.json is a configuration file used by Node.js npm projects.

It stores information such as:

Project name
Version
Scripts
Dependencies
DevDependencies
Main file
Description
License

It helps npm understand how the project is configured.

2. How do I create package.json?

Run:

npm init

npm will ask you questions and create the file.

For a faster setup, use:

npm init -y

3. What is the main property in package.json?

The main property identifies the main entry file of a package.

Example:

{
    "main": "index.js"
}

However, the main property by itself does not create an npm start command. To start your application with npm start, define a script:

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

4. What is the scripts section in package.json?

The scripts section contains commands that you can run using npm.

Example:

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

You can run:

npm start

or:

npm run dev

5. What is the difference between dependencies and devDependencies?

dependencies contains packages needed by the application.

Example:

"dependencies": {
    "express": "^5.0.0"
}

devDependencies contains packages mainly needed during development.

Example:

"devDependencies": {
    "nodemon": "^3.0.0"
}

6. What does "type": "module" do in package.json?

It tells Node.js to treat .js files in that package scope as ES Modules.

This allows syntax such as:

import express from "express";

and:

export function add(a, b) {
    return a + b;
}

Without "type": "module", Node.js commonly treats .js files as CommonJS unless another module configuration applies.

7. Should package.json be included when sharing a Node.js project?

Yes. package.json should normally be included because it tells npm which packages and scripts the project uses.

The node_modules folder is normally not shared or committed to version control. Another developer can usually recreate it by running:

npm install

inside the project directory.

Written by Shubhranshu Shekhar, who has trained 20000+ students in coding.

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