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JavaScript Basic Program

Let us write a complete Hello World program in JavaScript and understand each line.

<!DOCTYPE html>
<html lang="en">
<head>
  <title>Hello World</title>
</head>
<body>

  <h1>My first JavaScript page</h1>

  <script>
    console.log("Hello, World!");
    alert("Hello, World!");
  </script>

</body>
</html>

How it works

  • The <script> tag tells the browser that the code inside is JavaScript.
  • console.log() prints a message in the browser console (open it with F12).
  • alert() shows a pop-up box with the message. The page waits until you click OK.
  • Each statement ends with a semicolon ;.

The console shows:

Output of the above program is

Hello, World!

The same program in an external file

<script src="app.js"></script>
// app.js
console.log("Hello, World!");
Note: alert() is fine to learn, but real websites avoid it because it blocks the visitor. Use console.log() for testing and the DOM for showing messages on the page.

Summary

  • JavaScript runs inside a <script> tag or in a linked file.
  • console.log() and alert() show a message.
  • Next: JavaScript Output.

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