What Is JavaScript?

JavaScript is a programming language that adds behavior and interactivity to web pages. HTML defines the structure of a page, CSS controls how it looks, and JavaScript makes it respond to user actions. With JavaScript, you can:

• React to button clicks;
• Update content without reloading the page;
• Show or hide elements;
• Build dynamic interfaces.

Most modern websites rely on JavaScript for features like dropdown menus, form validation, and live updates.

How JavaScript Works with HTML and CSS

These three technologies work together:

• HTML → structure;
• CSS → appearance;
• JavaScript → behavior.

Here is a simple example:

Clicking the button triggers JavaScript, which updates the text on the page.

Where JavaScript Runs

JavaScript runs directly in your browser. Every browser has a built-in engine that executes your code instantly. You don't need to install anything, just a browser and a place to write code.