Intro and Setup¶
What is Node.js?¶
Node.js is a runtime environment that allows JavaScript to run outside the browser using Chrome's V8 engine. It's designed for building fast, scalable, and efficient network applications — especially servers and CLI tools.
Key Features:¶
- Asynchronous and non-blocking
- Built on event-driven architecture
- JavaScript on the backend
- Fast execution (compiled to machine code)
- Access to built-in modules (fs, http, path, etc.)
How Node.js Works¶
Node.js uses an event loop and callback queue to handle I/O asynchronously:
- Single-threaded main loop
- Background threads for I/O via
libuv - Uses callbacks, Promises, or async/await for async flow
Use Cases¶
- REST APIs and backend servers
- Real-time apps (chat, games)
- File processing scripts
- Command-line tools
- Microservices architecture
Setting Up Node.js¶
1. Install Node.js¶
Download and install from: https://nodejs.org Choose the LTS version unless you need the latest features.
2. Verify Installation¶
node -v # Node.js version
npm -v # npm (Node Package Manager) version
Running JavaScript with Node¶
Create a file:
// hello.js
console.log("Hello from Node.js");
Run it in the terminal:
node hello.js
Node REPL (Read-Eval-Print Loop)¶
An interactive shell to execute JS line-by-line.
Start it:
node
Try this:
> 5 + 3
8
> const name = "Node"
> name.toUpperCase()
'NODE'
Exit:
Ctrl + C (twice)
Summary¶
| Feature | Purpose |
|---|---|
| Node.js | JavaScript runtime on the server |
| V8 Engine | Compiles JS to machine code |
| Event Loop | Handles async I/O without blocking |
| REPL | Test code interactively in terminal |
node file.js |
Run JS file outside the browser |