JavaScript is a programming language that runs code into your website. Sometimes, JavaScript can be malicious on some websites. However, you can use JavaScript to make games or even fancy designs that you could not do with CSS. JavaScript is often abbreviated as "JS".
File Extension
If you don't know what a file extension is, it's the end of a file that tells your computer what kind of file it is. For example, codeRED.txt. In this example, .txt is the file extension for plain text format. HTML uses the .js extension. Browsers such as Firefox or Epiphany already come with JavaScript. However, you can use an HTML document to run JavaScript.
To start programming inside JavaScript, you will need to make a .html document. Use this link to get ready for HTML HTML Introduction. In your new HTML document, you will have to type in:
<!DOCTYPE html>
<html>
<body>
<script>
</script>
</body>
</html>
In the <script> tags, that's where you code in JavaScript.