Detailed explanation of commonly used DOM methods in js-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

Detailed explanation of commonly used DOM methods in js

高洛峰

Feb 06, 2017 am 09:16 AM

Introducing several common methods of js DOM

Get element nodes getElementById getElementsByTagName getElementsByClassName

First write a simple web page for testing:

/*
　　test.html
*/
<!DOCTYPE html>
<html>
<head>
 <meta charset="utf-8">
 <title>test</title>
</head>
<body>
 <p id="contentId" style="width:500px; height: 30px;background-color: #ccc">这段的id是contentId。</p>
 <p class="contentClass" style="width:500px; height: 30px;background-color: #ccc">这段的class name是contentClass。</p>
</body>
</html>

1. getElementById

1. First define the variable var contentId = document.getElementById("contentId");

2. Then output the object contentId and return the element object with the id contentId (

). See the picture below:

js常用DOM方法详解

2. getElementsByTagName

1. Define the variable first var contentTag = document.getElementsByTagName("p");

　2. Then I output the contentTag, which returns two HTMLCollection [

] in total. One starts with # to represent the id, and the other starts with . to represent the Class name.

　3. Continue contentTag[0] Output

contentTag[ 1] Output

js常用DOM方法详解

##From this we can see getElementsByTagName What is returned is an array!

3. getElementsByClassName

1. var contentClass = document.getElementsByClassName("contentClass");

2. contentClass output HTMLCollection [ ] Return a An array of element objects, even if there is only one.

　 3. contentClass[0] output

js常用DOM方法详解

We also commonly use getAttribute, setAttribute, ChildNodes, nodeType, nodeValue, firstChild, and lastChild methods to obtain some information.

4. Use getAttribute and setAttribute to get and set attributes respectively:

js常用DOM方法详解 ##After changing the style attribute:

js常用DOM方法详解 5. Then this is childNOdes:

##That is to say,

When encountering block elements, there will be There is a newline character
, and the browser will treat it as a text node when looking for child nodes. It can also be seen from the figure that childNodes also returns an array. js常用DOM方法详解

What if it is

There are 12 types of nodeType values, and there are three commonly used ones: 1 represents element node, 2 represents attribute node, and 3 represents text node. js常用DOM方法详解

nodeValue can not only get the value of the text node, but also change the value of the text node.

The above is the entire content of this article. I hope that the content of this article can bring some help to everyone's study or work. I also hope to support the PHP Chinese website! js常用DOM方法详解

For more detailed explanations of commonly used DOM methods in js, please pay attention to the PHP Chinese website!

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Node.js Streams with TypeScriptApr 30, 2025 am 08:22 AM

Node.js excels at efficient I/O, largely thanks to streams. Streams process data incrementally, avoiding memory overload—ideal for large files, network tasks, and real-time applications. Combining streams with TypeScript's type safety creates a powe

Python vs. JavaScript: Performance and Efficiency ConsiderationsApr 30, 2025 am 12:08 AM

The differences in performance and efficiency between Python and JavaScript are mainly reflected in: 1) As an interpreted language, Python runs slowly but has high development efficiency and is suitable for rapid prototype development; 2) JavaScript is limited to single thread in the browser, but multi-threading and asynchronous I/O can be used to improve performance in Node.js, and both have advantages in actual projects.

The Origins of JavaScript: Exploring Its Implementation LanguageApr 29, 2025 am 12:51 AM

JavaScript originated in 1995 and was created by Brandon Ike, and realized the language into C. 1.C language provides high performance and system-level programming capabilities for JavaScript. 2. JavaScript's memory management and performance optimization rely on C language. 3. The cross-platform feature of C language helps JavaScript run efficiently on different operating systems.

Behind the Scenes: What Language Powers JavaScript?Apr 28, 2025 am 12:01 AM

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

The Future of Python and JavaScript: Trends and PredictionsApr 27, 2025 am 12:21 AM

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

Python vs. JavaScript: Development Environments and ToolsApr 26, 2025 am 12:09 AM

Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.

Is JavaScript Written in C? Examining the EvidenceApr 25, 2025 am 12:15 AM

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript's Role: Making the Web Interactive and DynamicApr 24, 2025 am 12:12 AM

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.

See all articles