Using Node.js to Run JavaScript

Section 1.2: Setting Up the Environment

Tutorial 1.2.3: Using Node.js to Run JavaScript

Using Node.js to Run JavaScript

Node.js is a JavaScript runtime that allows you to execute JavaScript code outside of the browser. It's an essential tool for modern development, especially for server-side applications and command-line scripts. This tutorial will guide you through installing Node.js and running JavaScript with it.

Why Use Node.js?

Run JavaScript Anywhere: Execute code on your computer, independent of the browser.
Server-Side Development: Build APIs and back-end services.
Access to npm: Use and manage libraries and tools through the Node Package Manager (npm).

Step-by-Step Guide

Download Node.js:

Visit the official Node.js website.
Download the LTS (Long Term Support) version for better stability.

Install Node.js:

Run the downloaded installer and follow the installation prompts.
Ensure that npm (Node Package Manager) is installed alongside Node.js (it usually is).

Verify Installation:

Open your terminal (Command Prompt, PowerShell, or any terminal on macOS/Linux).
Check the Node.js version:

     node -v

Check the npm version:

     npm -v

Running JavaScript with Node.js

Using the REPL (Read-Eval-Print Loop):

Open the terminal and type node to enter the Node.js interactive mode.
Type JavaScript directly:

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

Running a JavaScript File:

Create a new file named example.js and add the following code:

     console.log("Running JavaScript with Node.js!");

Save the file and run it with Node.js:

     node example.js

Output:

     Running JavaScript with Node.js!

Exploring Node.js Features

Accessing the File System:

Example of reading a file:

     const fs = require('fs');
     fs.readFile('example.txt', 'utf8', (err, data) => {
       if (err) throw err;
       console.log(data);
     });

Using npm:

Install a package:

     npm install lodash

Use it in your code:

     const _ = require('lodash');
     console.log(_.capitalize("hello world"));

Benefits of Using Node.js for JavaScript

Fast Execution: Powered by Google’s V8 engine.
Asynchronous and Event-Driven: Ideal for non-blocking applications.
Cross-Platform: Runs on Windows, macOS, and Linux.

// redisClient.js const redis = require("redis"); const client = redis.createClient({ url: process.env.REDIS_URL }); client.on("error", (err) => console.error("Redis error:", err)); client.connect(); module.exports = client;

// rateLimiter.js const client = require("./redisClient"); const rateLimiter = (limit = 100, windowSec = 3600) => { return async (req, res, next) => { const ip = req.ip; const key = `rate_limit:${ip}`; const current = await client.get(key); if (current !== null && parseInt(current) >= limit) { return res.status(429).json({ error: "Too many requests. Try later." }); } const multi = client.multi(); multi.incr(key); if (!current) { multi.expire(key, windowSec); } await multi.exec(); next(); }; }; module.exports = rateLimiter;

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Using Node.js to Run JavaScript

Section 1.2: Setting Up the Environment

Tutorial 1.2.3: Using Node.js to Run JavaScript