> For the complete documentation index, see [llms.txt](https://shsbt.gitbook.io/hack-the-web/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shsbt.gitbook.io/hack-the-web/build-with-the-basics/javascript.md).
# JavaScript
JavaScript is a programming language used to make websites interactive. While HTML creates the structure of the webpage and CSS styles it, JavaScript allows the page to **respond to user actions** like clicking buttons, typing in forms, or moving the mouse.
### Example of JavaScript:
Here’s a simple example where JavaScript is used to display an alert message when a button is clicked:
```html
My First JavaScript
Click the Button
```
#### Breaking It Down:
* **``**: This creates a button. When you click the button, it triggers the `sayHello` function.
* **`