What does javascript use to get dom elements?

Javascript method to get dom elements: 1. Use getElementById() to get the element based on the id; 2. Use getElementsByName() to get the element based on the name attribute; 3. Use getElementsByTagName() to get the element based on the tag name; 4. Use getElementsByClassName() to get elements based on the class name; 5. Use querySelector() to return the first element object based on the specified selector.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

js consists of three parts:

• ECMAScript: js syntax

• DOM: Document Object Model

• BOM: Browser Object Model

WebApi is a standard developed by the W3C organization. In WebApi we mainly Learning DOM and BOM is also a unique part of js for webapi. It is neither a unique category of js itself nor a part of js learning. However, before learning WebApi, you need the foundation of js as the basis of learning WebApi.

DOM

DOM Introduction: Document Object Model (DOM) is a standard programming interface recommended by the w3c group for processing extensible markup language (HTML or XML). w3c has defined a series of DOM interface, through which the content, structure and style of web pages can be changed.

• Document: A page is a document. Document is used in DOM to represent

• Element: All tags in the page are elements. In DOM Use element to represent

• node: All content in a web page can be regarded as a node (labels, attributes, text, comments, etc.). Use node in DOM to represent

Get DOM elements

How to get elements

• Get based on id, use getElementById () method to get the object with the id element

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• Get based on the name attribute: Use the getElementsByName() method to return the specified The object collection of the name attribute

document.getElementsByName('name')

• Get based on the tag name: Use the getElementsByTagName() method to return a collection of objects with the specified tag name.

 
 
花海
 
晴天
 
七里香
 
花海
 
晴天
 
 
 
花海2
 
晴天2
 
七里香2
 
花海2
 
晴天2
 
  

Note: Because what we get is a collection of objects, we need to traverse if we want to operate the elements. The element object obtained is dynamic

Acquired through the new method of HTML5

• getElementsByClassName('Type') Obtains elements according to the class name

// 1、使用 getElementByClassName 获取 class类名元素 var box = document.getElementsByClassName("box"); // 可以获取全部的 class名为 box的元素 console.log(box);

• querySelector('selector') Returns the first element object based on the specified selector

// 2、querySelector 返回指定选择器的第一个元素对象 切记：里面选择器需要添加 .box #nav var firstBox = document.querySelector('.box') // 只能获取第一个class名为 box 的元素 console.log(firstBox); var nav = document.querySelector('#nav') console.log(nav); var li = document.querySelector('li') // 获取的也是第一个 li 元素 console.log(li);

• querySelectorAll('selector') Returns all the specified selectors Collection of element objects

// 3、querySelectorAll 返回 全部的 li 元素 var allBox = document.querySelectorAll('li') console.log(allBox);

Special element acquisition (body, html)

• Get body element

// 1. 获取 body 元素 var bodyEle = document.body; console.log(bodyEle)

• Get html elements

// 2. 获取 HTML 元素 var htmlEle = document.documentElement; console.log(htmlEle)

Note: The key point is to remember several ways to get ordinary elements. Body and html are not commonly used, just for understanding.

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