JavaScript Introduction
JavaScript is the world's most popular programming language and the programming language of the Web.
JavaScript can update and change both HTML and CSS. It can calculate, manipulate, and validate data. JavaScript runs directly in the browser — no installation needed!
JavaScript is one of the 3 languages all web developers must learn:
- HTML — to define the content of web pages
- CSS — to specify the layout of web pages
- JavaScript — to program the behavior of web pages
Try It — JavaScript in Action
Click the JS tab to see the script. Then click Run and try clicking the button!
Preview
What Can JavaScript Do?
| Capability | Example |
|---|---|
| Change HTML content | element.innerHTML = "New text" |
| Change CSS styles | element.style.color = "red" |
| React to user actions | Button clicks, keyboard input |
| Validate form data | Check if an email looks correct |
| Fetch data from servers | Load new content without refreshing |
Tip: Open the JS tab in the editor and modify the
changeText()function to display your own custom message!