Example code for using HTML DOM to access JavaScript document elements-HTML Tutorial-php.cn

Example code for using HTML DOM to access JavaScript document elements

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Release： 2017-05-05 11:51:39

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Through the HTML DOM, all elements of the JavaScript HTML document can be accessed.

HTML DOM (Document Object Model)

When a web page is loaded, the browser creates the page's Document Object Model (Document Object Model).

The HTML DOM model is constructed as a tree of objects.

HTML DOM tree

Through the programmable object model, JavaScript has gained enough power to create dynamic HTML.

JavaScript can change all HTML elements in the page

JavaScript can change all HTML attributes in the page

JavaScript can change all CSS styles in the page

JavaScript is able to react to all events in the page

Find HTML elements

Usually, with JavaScript, you need to manipulate HTML elements.

In order to do this, you must first find the element. There are three ways to do this:

Find the HTML element by id

Find the HTML element by tag name

Find the HTML element by class name

Finding HTML elements by id

The simplest way to find HTML elements in the DOM is by using the element's id.

Example

This example looks for the element with id="intro":

[html] view plain copy
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "m.sbmmt.com/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
<html xmlns="m.sbmmt.com/1999/xhtml">  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
<title>无标题文档</title>  
</head>   
<body>  
<p id="intro">hello</p>  
<p>本例演示 <strong>getElementById</strong> 方法</p>  
  
<script>  
    x = document.getElementById("intro");  
    document.write(&#39;<p>id="intro" 的段落中的文本是：&#39; + x.innerHTML + &#39;</p>&#39;);  
</script>  
</body>  
</html>

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If the element is found, the method will return it as an object (in x) element.

If the element is not found, x will contain null.

Find HTML elements by tag name

Example

This example finds the element with id="main", and then finds all

elements in "main":

[html] view plain copy
<html xmlns=m.sbmmt.com/1999/xhtml">  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
<title>无标题文档</title>  
</head>  
  
<body>  
<div id="main">  
    <p>The DOM is very useful.</p>  
<p>本例演示 <b>getElementsByTagName</b> 方法。</p>  
</div>  
<script>  
    var x = document.getElementById("main");  
    var y = document.getElementsByTagName("p");  
    document.write(&#39;id 为 "main" 的 div 中的第一段落文本是：&#39; + y[0].innerHTML);  
</script>  
</body>  
</html>

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Finding HTML elements by class name does not work in IE 5,6,7,8.

【Related recommendations】

1. Free html online video tutorial

2. html development manual

3. php.cn original html5 video tutorial

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