JavaScript: Introduction

What is JavaScript?

JavaScript is the programming language of the web. It lets you add interactivity to HTML pages, respond to user actions, update the DOM, fetch data, and much more.

In the browser, JavaScript runs in the main thread alongside the rendering engine. You write code in <script> tags or separate .js files and the browser executes it.

A very short history of JavaScript

JavaScript was created by Brendan Eich in 1995 at Netscape in about 10 days. Standardized as ECMAScript (ES) by ECMA, the language matured through ES3 (1999), ES5 (2009), and the big ES2015 (ES6) update with classes, modules, and more. Since then, JS evolves yearly, adding features like async/await, optional chaining, and modern standard library improvements.

Hello, JavaScript

Open your browser devtools (F12) and try typing this in the Console:

console.log('Hello, JavaScript!');

Or embed it in a page:

<script>
console.log('Hello from a script tag');
</script>

Where we'll go next

• Variables & Types
• Control Flow
• Functions
• DOM & Events