Welcome to JavaScript: The Language of the Web

JavaScript was created by Brendan Eich in 1995, originally in just ten days, to make web pages interactive. Three decades later it has grown into one of the most widely used programming languages in the world — it runs in every major browser, and through Node.js it also runs on servers, powering companies like Netflix, PayPal, and LinkedIn on the backend as well as the frontend.

What makes JavaScript unique among mainstream languages is that it is the only language that runs natively in every web browser, with no installation required by the visitor. If you want a web page to respond to a click, validate a form before it’s submitted, or update content without reloading the page, JavaScript is how that happens.

Your first script

Create an index.html file and add a script tag, or — faster for experimenting — open your browser’s DevTools console (press F12, or right-click any page and choose Inspect, then click the Console tab) and type directly:

console.log("Hello, Tutoline!");
const name = prompt("What's your name?");
console.log(`Nice to meet you, ${name}`);

Where JavaScript runs

In the browser, JavaScript can read and change the page (the DOM), react to user input, store data locally, and talk to servers over the network. With Node.js installed, the exact same language runs scripts and full backend servers outside the browser entirely — the syntax you learn in this course applies in both environments, though some built-in objects differ (a browser has window and document; Node.js has process and file system access instead).

Installing Node.js (optional, for running scripts outside the browser)

# check if it's already installed:
node --version

# if not, download the installer from nodejs.org, or:
# macOS: brew install node
# Windows: winget install OpenJS.NodeJS

Once installed, you can save a file as hello.js and run it directly with node hello.js — no browser needed, exactly like running a Python script.

What you’ll build across this course

By the end of this course you’ll be comfortable with variables and functions, working with data via arrays and objects, updating a real web page through the DOM, handling asynchronous operations like network requests, and writing the kind of closures, classes, and error handling used in production JavaScript.

Tip: keep DevTools open while you learn — it’s the fastest feedback loop you have, and every error message it shows you is worth reading carefully rather than dismissing.