JavaScript — Introduction

What is JavaScript?

JavaScript is the programming language of the web. HTML gives a page structure and CSS makes it pretty — JavaScript makes it alive:

• Menus that open when you click
• Forms that check your email format instantly
• Slideshows, games, live chat
• Loading new data without refreshing

It's also one of the only languages that runs in every browser on Earth, which makes it an excellent first language.

Fun fact: despite the name, JavaScript has nothing to do with Java. The name was marketing, back in 1995.

Your first line

Open any web page, press F12, click the Console tab, and type:

alert("Hello! I am JavaScript.");

Press Enter. Congratulations — you just ran real code.

A tiny example in a page

<button onclick="greet()">Say hello</button>

<script>
  function greet() {
    alert("Hello there!");
  }
</script>

Click the button, and the function runs. That's the core idea: something happens → your code responds.

What you'll learn here

1. Variables — remembering values
2. Conditions — making decisions (if)
3. Loops — repeating work
4. Functions — packaging code for reuse
5. Arrays & objects — organizing data
6. The DOM — controlling the actual web page

JavaScript rewards experimentation. Break things, read the error message, fix them. That is programming.