Node.js Basics

Node.js is an open-source, cross-platform, back-end JavaScript runtime environment that executes JavaScript code outside a web browser. It uses an event-driven, non-blocking I/O model, making it lightweight and efficient.

Node.js Information

Node.js is primarily used for building scalable network applications. It's popular for APIs, real-time applications, and microservices. Its package manager, npm (Node Package Manager), provides access to a vast ecosystem of modules.

Download and Installation

Download Node.js from the official website. The installer will guide you through the process. Make sure to select the correct installer for your operating system.

Path Variable Setup

Adding Node.js to your system's PATH environment variable allows you to run Node.js commands from any directory in your command prompt or terminal.

Running Node.js exe

After installation, you can run the Node.js executable directly from the installation directory. However, adding it to the PATH is recommended for easier access.

Using cmd

Once the PATH is set up, you can open your command prompt or terminal and type node -v to verify the installation. This command will display the installed Node.js version.

REPL Terminal

REPL (Read-Eval-Print Loop) is an interactive environment provided by Node.js for experimenting with JavaScript code. You can access it by simply typing node in your terminal.

Examples

> console.log("Hello from REPL!");
Hello from REPL!
> let x = 10;
undefined
> x + 5;
15

Running First Node.js Code

Create a file (e.g., hello.js) with the following code:

console.log("Hello, world from Node.js!");

Run this code from your terminal using node hello.js. The output will be displayed in the console.

Node.js Examples

Global Variables

In Node.js, some variables are globally accessible. global is a global object. __dirname gives the current directory. __filename gives the current file name.

console.log(__dirname);
console.log(__filename);

Differences between Browser JavaScript and Node.js

Browser JavaScript runs in a web browser environment, while Node.js runs on a server. Browser JavaScript has access to the browser's APIs (DOM, etc.), while Node.js has access to server-side APIs (e.g., file system access). Node.js uses a different event loop model compared to most browsers.

Summary

• Node.js is a JavaScript runtime for server-side development.
• It uses an event-driven, non-blocking I/O model.
• It is known for its lightweight and efficient nature.
• The Node Package Manager (npm) provides access to a large community of modules.
• Node.js has global variables like global, __dirname, and __filename.
• It is different from browser JavaScript in its execution environment and API access.