Detailed explanation of how to create, use and delete dom node instances in JavaScript-JS Tutorial-php.cn

Detailed explanation of how to create, use and delete dom node instances in JavaScript

伊谢尔伦

Release： 2017-07-20 13:26:38

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Create node

In order to create a new node, you can use createElement and createTextNode. If the new creation is completed, you can use appendChild() to add the node to the DOM tree.

Create an element P and set the innerHTML attribute

var myp = document.createElement(&#39;p&#39;); 
myp.innerHTML = &#39;yet another&#39;;

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After the element P is created, you can modify and add attributes at will

myp.style.border = &#39;2px dotted blue&#39;

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Next, you can use appendChild to add new nodes to the DOM tree.

document.body.appendChild(myp)

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Methods of using DOM
It is indeed very simple to use the innerHTML method. We can use the pure dom method to achieve the above functions.

Create a new text node (yet another)
Create a new paragraph
Place the text node Add to paragraph.
Add paragraphs to body

// 创建p 
var myp = document.createElement(&#39;p&#39;); 
// 创建一个文本节点 
var myt = document.createTextNode(&#39;one more paragraph&#39;) 
myp.appendChild(myt); 
// 创建一个STRONG元素 
var str = document.createElement(&#39;strong&#39;); 
str.appendChild(document.createTextNode(&#39;bold&#39;)); 
// 把STRONG元素添加到P中 
myp.appendChild(str); 
// 把P元素添加到BODY中 
document.body.appendChild(myp); 
//结果<p>one more paragraph<strong>bold</strong></p> 
 cloneNode()

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Another way to create a new node is, we You can use cloneNode to copy a node. cloneNode() can pass in a boolean parameter. If true, it means a deep copy, including its child nodes, if false, it only copies itself.

First get the element to be copied.

var el = document.getElementsByTagName(&#39;p&#39;)[1];//<p><em>second</em> paragraph</p>

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No need to make a deep copy first.

document.body.appendChild(el.cloneNode(false))

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We found that the page did not change, because only the element p was copied. The same effect as below.

document.body.appendChild(document.createElement(&#39;p&#39;));

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If deep copy is used, all child nodes including p below will be copied. Including text nodes and EM elements of course.

document.body.appendChild(el.cloneNode(true))

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insertBefore()
Using appendChild is to add the element to the end. The insertBefore method can more precisely control the position of inserted elements.

elementNode.insertBefore(new_node,existing_node)

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Example

document.body.insertBefore( 
 document.createTextNode(&#39;boo!&#39;), 
 document.body.firstChild 
);

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It means to create a new text node and use it as the first node of the body element .
Delete Node

To delete a node from the DOM tree, we can use removeChild(). Let’s take a look at the HTML to be operated

<body> 
 <p class="opener">first paragraph</p> 
 <p><em>second</em> paragraph</p> 
 <p id="closer">final</p> 
 <!-- and that&#39;s about it --> 
</body>

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Let’s take a look at the following code. Delete the second paragraph

var myp = document.getElementsByTagName(&#39;p&#39;)[1]; 
var removed = document.body.removeChild(myp);

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The removed node is the deleted node. The deleted node can still be used in the future.

We can also use the replaceChild() method. This method is to delete a node and replace it with another node. After performing the last node deletion operation, the result is as follows

<body> 
 <p class="opener">first paragraph</p> 
 <p id="closer">final</p> 
 <!-- and that&#39;s about it --> 
</body>

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Let’s take a look at the use of replaceChild. We replace the second p

var replaced = document.body.replaceChild(removed, p);

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with the last deleted node, which is the same as removeChild returns. Replaced is the removed node. Now the result is

<body> 
 <p class="opener">first paragraph</p> 
 <p><em>second</em> paragraph</p> 
 <!-- and that&#39;s about it --> 
</body>

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