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Chapter 7: Introduction to JavaScript: Bringing Interactivity to Your Web Pages
Welcome to Chapter 7! So far, we've explored the structure and styling of web pages using HTML and CSS. Now, it's time to dive into JavaScript,
the programming language that adds interactivity and dynamic content to your web pages.
7.1 What is JavaScript?
JavaScript (JS) is a high-level, interpreted scripting language that enables you to create dynamically updating content, control multimedia,
animate images, and much more. Essentially, JavaScript is what makes your web pages interactive and engaging.
7.2 How JavaScript Works with HTML and CSS
JavaScript can be included in web pages using the <script> tag. It can be placed either in the <head> or at the end of
the <body> (recommended for faster loading). JavaScript interacts with HTML and CSS to manipulate the Document Object Model
(DOM) - the structure of the web page as understood by the browser.
<!DOCTYPE html>
<html>
<head>
<!-- Head content -->
</head>
<body>
<!-- Body content -->
<script>
// JavaScript code goes here
</script>
</body>
</html>
7.3 Basic JavaScript Syntax
JavaScript consists of statements and expressions that are executed by the web browser. A basic understanding of
programming concepts like variables, data types, operators, and functions is essential.
Alert Message
<script>
alert("Welcome to my website!");
</script>
7.4 Variables
Variables are used to store data values. JavaScript uses the var, let, and const keywords to declare variables.
let message = 'Hello, World!';
alert(message);
7.5 Functions
Functions are blocks of code designed to perform a particular task, and they are executed when something invokes them.
function greet() {
alert('Hello, World!');
}
greet();
7.6 Manipulating the DOM
JavaScript can change all the HTML elements in the page, change all the HTML attributes in the page, change all the CSS styles
in the page, remove existing HTML elements and attributes, add new HTML elements and attributes, react to all existing HTML
events in the page, and create new HTML events in the page.
Changing HTML content
document.getElementById("demo").innerHTML = "Hello JavaScript!";
7.7 Event Handling
JavaScript can be used to respond to events on a web page, like clicks, mouse movements, and keyboard actions.
HTML button with JavaScript click event
<button onclick="alert('Hello!')">Click Me!</button>
7.8 JavaScript and Forms
JavaScript is commonly used in forms to validate user input. It can check user entries before they are sent to the server,
reducing server load and providing a better user experience.
Checking if a field is empty
function validateForm() {
let x = document.forms["myForm"]["fname"].value;
if (x == "") {
alert("Name must be filled out");
return false;
}
}
Summary
In this chapter, you've gained an introduction to JavaScript and how it can be used to add interactivity to your web pages.
JavaScript is a powerful tool that, when combined with HTML and CSS, allows for the creation of dynamic, interactive, and engaging web experiences.
Up Next: In the following chapters, we'll explore more JavaScript concepts in detail, including advanced event handling,
working with APIs, and asynchronous programming. As you progress, remember that practical application and experimentation are key to understanding and mastering JavaScript.
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