Memahami Model Objek Dokumen (DOM)-tutorial js-php.cn

Memahami Model Objek Dokumen (DOM)

Susan Sarandon

Lepaskan： 2024-10-13 06:18:02

asal

846 orang telah melayarinya

Understanding the Document Object Model (DOM)

The Document Object Model (DOM) is a crucial concept for web developers, as it defines the structure of a document and allows for dynamic interaction with HTML and XML documents. This guide will help you understand the DOM, its structure, and how to manipulate it using JavaScript.

What is the DOM?

Definition: The DOM is a programming interface for web documents. It represents the document as a tree of objects, allowing scripts to update the content, structure, and style of a document while it's being viewed.
Tree Structure: The DOM represents a document as a tree of nodes. Each node represents a part of the document, such as an element, attribute, or text.

DOM Structure

Node Types

Document Node: The root of the DOM tree. Represents the entire document.
Element Node: Represents an HTML element (e.g.,
,
, ).

Text Node: Represents the text within an element.

Attribute Node: Represents the attributes of an element (e.g., class, id).

Comment Node: Represents comments in the HTML.

Example DOM Tree

<!DOCTYPE html>
<html>
<head>
    <title>My Page</title>
</head>
<body>
    <h1>Hello, World!</h1>
    <p>This is a paragraph.</p>
</body>
</html>

Salin selepas log masuk

DOM Representation:

Document
├── html (Element)
│   ├── head (Element)
│   │   └── title (Element)
│   │       └── "My Page" (Text)
│   └── body (Element)
│       ├── h1 (Element)
│       │   └── "Hello, World!" (Text)
│       └── p (Element)
│           └── "This is a paragraph." (Text)

Salin selepas log masuk

Accessing the DOM

Selecting Elements

getElementById: Selects a single element by its ID.

  const element = document.getElementById('myId');

Salin selepas log masuk

getElementsByClassName: Returns a live HTMLCollection of elements with the specified class name.

  const elements = document.getElementsByClassName('myClass');

Salin selepas log masuk

getElementsByTagName: Returns a live HTMLCollection of elements with the specified tag name.

  const elements = document.getElementsByTagName('div');

Salin selepas log masuk

querySelector: Selects the first element that matches a CSS selector.

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

Salin selepas log masuk

querySelectorAll: Returns a static NodeList of all elements that match a CSS selector.

  const elements = document.querySelectorAll('div.myClass');

Salin selepas log masuk

Manipulating Elements

Changing Content:

  const element = document.getElementById('myId');
  element.textContent = 'New Content';

Salin selepas log masuk

Changing Attributes:

  const element = document.getElementById('myId');
  element.setAttribute('class', 'newClass');

Salin selepas log masuk

Changing Styles:

  const element = document.getElementById('myId');
  element.style.color = 'blue';

Salin selepas log masuk

Creating and Appending Elements:

  const newElement = document.createElement('div');
  newElement.textContent = 'I am a new div';
  document.body.appendChild(newElement);

Salin selepas log masuk

Removing Elements:

  const element = document.getElementById('myId');
  element.parentNode.removeChild(element);

Salin selepas log masuk

DOM Events

Events are actions or occurrences that happen in the browser, and you can respond to them with event handlers.

Adding Event Listeners

const button = document.getElementById('myButton');
button.addEventListener('click', function() {
    alert('Button clicked!');
});

Salin selepas log masuk

Common Events

click: Triggered when an element is clicked.
mouseover: Triggered when the mouse hovers over an element.
keydown: Triggered when a key is pressed down.
submit: Triggered when a form is submitted.

Conclusion

Understanding the DOM is essential for web development, as it provides a way to interact with and manipulate web pages. Mastering DOM manipulation will allow you to create dynamic and interactive web applications.

Feel free to dive deeper into the documentation and experiment with the various methods and properties available in the DOM API. Happy coding!

Atas ialah kandungan terperinci Memahami Model Objek Dokumen (DOM). Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!