JavaScript Introduction

Definition: JavaScript is the programming language of the web. It runs inside every browser and makes web pages interactive — responding to clicks, updating content, validating forms, and more.

HTML provides the structure of a page and CSS styles it, but only JavaScript makes it do things. It needs no installation — your browser already runs it.

What can JavaScript do?

• Change a page's content and style after it loads
• React to clicks, typing, and scrolling
• Load data from servers in the background
• Build full web apps, games, and even server software

Showing output

While learning, we display results with console.log(), which prints to the console — and to the Output box below.

Example — your first program

console.log("Hello, World!");
console.log("I am learning JavaScript");

Press Run, then change the text and run it again.