What is Node.js?

Learn that Node.js is a V8-based runtime and the event loop.

What is Node.js?

Node.js is a runtime that runs JavaScript outside the browser. It is used to write server applications, command-line tools and scripts.

It is built on Google Chrome's V8 engine and uses the libuv library to perform file and network operations asynchronously. This way it can handle thousands of connections at once efficiently.

Today Node.js 22 LTS is the recommended version. This course uses ES modules syntax.

V8 and the event loop

V8 is Google's open-source JavaScript engine. It is written in C++ and compiles JavaScript into machine code. Node.js uses V8 to execute JavaScript quickly.

The event loop enables Node.js to work asynchronously. When an operation finishes, a callback is triggered. This way the main flow can do other work without blocking.

This model provides high throughput, especially for network and database operations.

Exercise Write your first output

Use console.log to print Node.js is running to the screen.

Show example solution

console.log("Node.js is running");

Test yourself

What is Node.js built on?
- The C# runtime
- The Python interpreter
- The Java virtual machine
- The V8 JavaScript engine
Show answer

The V8 JavaScript engine — Node.js is built on the V8 engine.
Match the concepts

Node.js

Runtime
V8

JavaScript engine
libuv

Event loop library
npm

Package manager

Run command

To run a JavaScript file, you type ____ file.js in the terminal.

Show answer

To run a JavaScript file, you type node file.js in the terminal.

Next lesson: Your first program

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