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

Detailed explanation of commonly used DOM methods in js

高洛峰

Release： 2017-02-06 09:16:06

Original

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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>

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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.

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