Understanding Document Object Model (DOM) in JavaScript

DDD

Release： 2024-09-19 01:06:02

Original

842 people have browsed it

Understanding Document Object Model (DOM) in JavaScript

Hello, Amazing JavaScript Devs ?

Browsers provide a programming interface called the Document Object Model (DOM) that lets scripts—JavaScript in particular—interact with the layout of a web page. A web page's Document Object Model (DOM), a hierarchical tree-like structure that arranges the page's components into objects, is created by the browser as it loads. A document's style, organization, and content may all be dynamically accessed and altered with the help of this paradigm.

Using the DOM to interact

Many operations can be carried out on the Document Object Model (DOM) by JavaScript, including:

Modifying the content of HTML elements
Adding or removing elements and attributes
Responding to user events like clicks or key presses
Creating new events within the page

Example

You may use JavaScript to alter an element's content by targeting it with the document.getElementById() function and then changing the element's innerHTML property:

// Modify an element's content, access it using its ID
document.getElementById("myElement").innerHTML = "New content";

Copy after login

DOM Structure

The document object is at the base of the DOM, which is organized as a tree of objects. Every HTML element is represented as a node in the tree, and these nodes are capable of having related events, methods, and properties. By offering ways to navigate and work with these nodes, the DOM enables scripts to alter the page in real time.

Here's a basic example of what a typical HTML document's DOM tree may look like:

document
├── html
│ ├── head
│ │ └── title
│ └── body
│ ├── h1
│ └── p

Copy after login

DOM's Function in Web Development

The DOM is essential to web development for a number of reasons.

It makes it possible to create dynamic and interactive web pages by letting scripts change a page's style and content in response to user input.
It ensures uniformity across platforms by offering a standardized interface for various browsers to interact with and manipulate online pages.
Single-page applications (SPAs) depend on the DOM to refresh the page without requiring a reload, hence it is critical to their operation.

DOM Levels and Standards

The World Wide Web Consortium (W3C) maintains the DOM standard, which guarantees its dependability and consistency across various web browsers and systems. The standard is broken down into various sections and levels, including:

The foundational paradigm for all document types is * Core DOM:.
The XML document model is called XML DOM.
HTML DOM: The model was created especially for HTML files.

More capabilities and functionality are added with every DOM standard version, enabling more intricate online document manipulations and interactions.

Real-World Illustration of DOM Manipulation

Here's a real-world illustration of how you could communicate with an HTML document using the DOM:

<!DOCTYPE html>
<html>
<head>
<title>DOM Example</title>
</head>
<body>
<h1 id="header">Hello, World!</h1>
<button onclick="changeHeader()">Change Header</button>

<script>
function changeHeader() {
// Use the DOM to access and modify the h1 element
var header = document.getElementById("header");
header.textContent = "DOM Manipulation in Action!";
header.style.color = "blue";
}
</script>
</body>
</html>

Copy after login

In this example, clicking the button calls the changeHeader() function, which uses the DOM to access the

element by its ID. It then changes the text content and the color of the header.

Essential DOM Techniques

1. Query Selection

Use document.querySelector() to grab elements with pinpoint accuracy.

Explanation: querySelector() allows you to select elements using CSS selectors, making it a powerful and flexible way to access DOM Elements.

Example

// Select the first element with class 'myClass'

const element = document.querySelector('.myClass');

// Select a specific element by ID
const header = document.querySelector('#header' );

// Select the first <p> inside a <div>
const paragraph = document.querySelector('div p');

Copy after login

2. Dynamic Content

Modify innerHTML or textContent to update page content on the fly.

Explanation: innerHTML or textContent allows you to dynamically change the elements' content, enabling interactive and responsive web pages.

Example

// Using innerHTML (can include HTML tags)

document.querySelector('#myDiv').innerHTML = '<strong>New content!</strong>';

// Using textContent (plain text only, safer for user inputs)

document.querySelector('#myParagraph').textContent = 'Updated text content';

Copy after login

3. Event Listening

Attach addEventListener() to elements for interactive user Experiences.

Explanation: addEventListener() lets you respond to user actions like clicks, key presses, or mouse movements, creating interactive web applications.

Example

const button = document.querySelector('#myButton' );

button. addEventListener( 'click', function( ) {
     alert( 'Button clicked!')
});

// Using arrow function
document.addEventListener('keydown', (event) => {
     console. log( 'Key pressed:', event.key);
});

Copy after login

4. DOM Traversal

Navigate the DOM tree with parentNode, children and siblings properties.

Explanation: DOM Traversal allows you to move through the document structure, accessing related elements based on their position in the DOM tree.

Example

const child = document.querySelector('#childElement');

// Access parent
const parent = child.parentNode;

// Access siblings
const nextSibling = child.nextElementSibling;
const prevSibling = child.previousElementSibling;

// Access children
const firstChild = parent.firstElementChild;
const allChildren = parent.children;

Copy after login

Conclusion

The DOM is a powerful tool in JavaScript that enables developers to create rich, interactive web experiences. By understanding and utilizing the DOM, developers can control the behavior and appearance of web pages, making them more engaging and responsive to user interactions.

The above is the detailed content of Understanding Document Object Model (DOM) in JavaScript. For more information, please follow other related articles on the PHP Chinese website!