1️⃣ package.json

• The main metadata file for your project.
• Lists your project’s name, version, scripts, and dependencies (under "dependencies" and "devDependencies").
• Example snippet:

{
  "name": "my-app",
  "version": "1.0.0",
  "dependencies": {
    "express": "^4.18.2"
  }
}

2️⃣ package-lock.json

• Automatically generated or updated by npm when you run npm install.
• Records the exact versions of every package and its dependencies, including nested packages.
• Guarantees consistent installs across different environments (e.g., on your teammate’s machine or in production).

3️⃣ node_modules/

• A folder where npm installs all your packages and their dependencies.
• Its structure includes:
  • Top-level folders for each direct dependency you listed in package.json.
  • Nested folders for transitive dependencies (packages your dependencies depend on).
  • Each package folder includes its own package.json, JS files, and sometimes binary files.

my-app/ ├── package.json ├── package-lock.json └── node_modules/ ├── express/ │ ├── package.json │ └── ... (code files) └── accepts/ ├── package.json └── ... (another package express depends on)

✅ What this structure enables:

• Running require('express') or import express from 'express' finds the module in node_modules/express.
• npm uses node_modules and package-lock.json to manage consistent versions across installs.

🔥 Quick notes:

• If you delete node_modules/ and package-lock.json, running npm i again will restore them based on package.json.