npm & package.json

This lesson covers npm & package.json. You do not need to memorize everything. Understand the flow first.

What you will learn

• What npm & package.json means — in normal words, not textbook words
• How it works step by step
• Code you can run today on your laptop
• Where teams use this in real projects

Before you start

• Software: Node.js LTS from nodejs.org, VS Code, and a terminal
• Knowledge: Lessons 1–3 in this course
• Previous lesson: Installing Node.js — Complete Guide

Explain it simply

npm is Node's package manager. package.json is a small JSON file that lists your project name, scripts, and dependencies.

Why developers use this

• Share exact dependency versions with your team
• Run scripts like npm start
• Install packages with npm install express

How it works (step by step)

1. You write JavaScript in a .js file about npm & package.json.
2. You run it with node filename.js in the terminal.
3. Node prints output or starts a server depending on the lesson.
4. You change one line, run again, and see what changed — that is how you learn.

Code example — type this yourself

npm init -y
npm install express
npm install --save-dev nodemon

npm init -y creates package.json. install adds packages to node_modules and records them in package.json.

What each part does

• npm init -y — Line 1: runs as written.
• npm install express — Line 2: runs as written.
• npm install --save-dev nodemon — Line 3: runs as written.

Real life: where npm & package.json shows up

A startup team uses npm & package.json when they bootstrap their first API. The developer runs a small script on a laptop, stores config in .env, and splits code into modules before the app grows. Start small: one feature working beats a perfect architecture on paper.

Try it yourself — hands-on

1. Create a folder and run npm init -y
2. Open package.json and read the fields
3. Run npm install express and check node_modules

Common mistakes (avoid these)

• Deleting package-lock.json — it keeps installs reproducible.

Interview note

Interviewers often ask: “What is npm & package.json?” Answer in one sentence, then give a tiny example you actually ran.

Summary

• package.json describes your project
• npm install adds libraries
• Use --save-dev for tools used only while developing