🤖 What happens when you run npm install express?

✅ 1. npm = Node Package Manager

• It's a tool that helps you download and manage libraries (packages) in your Node.js project.
• So when you run npm install express, npm fetches the express package from the npm registry (https://registry.npmjs.org).

📂 2. What exactly happens under the hood?

When you type:

bash
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npm install express

👉 NPM does the following:

1. Checks if express is already present in node_modules
2. If not, downloads the latest version of express
3. Saves the code of express into:

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your-project/
  └── node_modules/
        └── express/

1. Adds "express": "^x.x.x" in your package.json under dependencies
2. Updates the package-lock.json with exact version details (for reproducibility)

🔗 3. Express itself uses other packages (dependencies)

Yes, Express is not a single file. It's made by developers using other small packages like:

• body-parser