JavaScript can be integrated into an HTML document in several ways.

 

Inline JavaScript

Inline JavaScript is written directly within your HTML elements. It’s used to handle simple, quick JavaScript functionality.

<button onclick="alert('Hello, World!');">Click me</button>

 

Internal JavaScript

Internal JavaScript is written inside the <script> tags in the HTML document. This is useful when the JavaScript code is not too large.

<script>
function greet() {
    alert('Hello, World!');
}
</script>
<button onclick="greet();">Click me</button>

 

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Your Web Page Title</title>

<!-- Inline JavaScript -->
<script>
// Your JavaScript code goes here
function greet() {
    alert('Hello, World!');
}
</script>
</head>
<body>
<!-- Your content goes here -->

<!-- Call the JavaScript function -->
<button onclick="greet()">Click me</button>
</body>
</html>

 

External JavaScript

External JavaScript is written in a separate file with a .js extension. This file is then linked to the HTML document using the <script> tag with the src attribute. This is useful when you have a large amount of JavaScript code or when you want to use the same JavaScript code in multiple HTML files.

<script src="script.js"></script>

 

In the script.js file:

function greet() {
    alert('Hello, World!');
}

 

In the HTML file:

<button onclick="greet();">Click me</button>

 

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Your Web Page Title</title>

<!-- External JavaScript -->
<script src="script.js"></script>
</head>
<body>
<!-- Your content goes here -->

<!-- Call the JavaScript function -->
<button onclick="greet()">Click me</button>
</body>
</html>