🌐 JavaScript in Browsers
JavaScript is primarily used in web browsers to make web pages interactive. Every modern browser has a built-in JavaScript engine that interprets and executes JavaScript code directly on the user’s device (client-side).
🧠 How JavaScript Works in a Browser:
- When a web page is loaded, the browser reads the HTML, CSS, and JavaScript.
- The JavaScript engine parses and runs the JavaScript code line by line.
- It interacts with the browser’s Document Object Model (DOM) to update page content dynamically.
- It responds to user actions such as clicks, input, scrolling, etc.
🛠️ Popular Browser JavaScript Engines:
- Chrome: V8 Engine
- Firefox: SpiderMonkey
- Safari: JavaScriptCore (a.k.a. Nitro)
- Edge (Chromium-based): V8 Engine
- Opera: V8 Engine
💡 Example: JavaScript in an HTML Page
<!DOCTYPE html>
<html>
<head><title>JavaScript in Browser</title></head>
<body>
<h2>Welcome!</h2>
<button onclick="sayHello()">Click Me</button>
<script>
function sayHello() {
alert("Hello from JavaScript!");
}
</script>
</body>
</html>
This example shows how JavaScript runs in the browser and responds to user events like button clicks.
