Comprehensive JavaScript node operations in one article

This article brings you relevant knowledge about javascript, which mainly introduces related issues about node operations, including parent nodes, child nodes, sibling nodes, adding, deleting and copying nodes. Let’s take a look at the content below. I hope it will be helpful to everyone.

[Related recommendations: javascript video tutorial, web front-end]

In our web page, In addition to using the methods provided by DOM to obtain nodes, you can also use the hierarchical relationship of nodes to obtain nodes. They are relatively simple. Let’s summarize them today!

Node Overview

All content in a web page is a node (label, attribute, text, comment, etc.). In the DOM, node is represented by node.
All nodes in the HTML DOM tree are accessible through JavaScript, and all HTML elements (nodes) can be modified, created or deleted.

Generally, nodes have at least three basic attributes: nodeType (node ​​type), nodeName (node ​​name) and nodeValue (node ​​value).

• The element node nodeType is 1
• The attribute node nodeType is 2
• The text node nodeType is 3 (text nodes include text, spaces, newlines, etc.)

In our actual development, node operations mainly operate on element nodes.

Node level

Using the DOM tree, nodes can be divided into different hierarchical relationships. The most common one is the hierarchical relationship between father, son, and brother.

1. Parent node

node.parentNode

• The parentNode property can return the parent node of a node, note that it is the nearest parent node.
• If the specified node has no parent node, return null.

<p>
        </p><p></p>
    
    <script>
        var son = document.querySelector(".son");
        console.log(son.parentNode);
    </script>

2. Child nodes

1.node.childNodes (standard)

node .childNodes returns a collection containing the child nodes of the specified node. This collection is an immediately updated collection.

        
• 我是li
        
• 我是li
        
• 我是li
        
• 我是li
    

    <script> var ul = document.querySelector(&#39;ul&#39;); // 子节点childNodes 所有子节点，包含元素节点，文本节点等。 console.log(ul.childNodes); </script>

Why are there five text nodes here? They actually correspond to five line breaks. See the picture below:

These five line breaks are text nodes. Plus four li element nodes, a total of 9

Note: The return value contains all child nodes, including element nodes, text nodes, etc.
If you only want to get the element nodes inside, you need to handle it specially. So we generally do not advocate the use of childNodes.

	var ul = document.querySelector('ul');
	for (var i = 0;i

2.node.children (non-standard)

node.children is a read-only property that returns all child element nodes. It only returns child element nodes, and other nodes are not returned (this is what we focus on).
Although children is a non-standard, it is supported by various browsers, so we can use it with confidence.

        
• 我是li
        
• 我是li
        
• 我是li
        
• 我是li
    

    <script> var ul = document.querySelector(&#39;ul&#39;); console.log(ul.children); </script>

3. The first child node and the last child node

1.node. firstChild
2.node. lastChild
firstChild returns the first child node. If it cannot find it, returns null. The same applies to lastChild. Likewise, all nodes are included.

3.node. firstElementChild
firstElementChild returns the first child element node, or null if not found.
4.node. lastElementChild
lastElementChild returns the last child element node, or null if not found.

Note: These two methods have compatibility issues and are only supported by IE9 and above.

5.node.children[0]
5.node.children[node.children.length - 1]
Note: The actual development method is not compatible Sexual issues.

        
• 我是li
        
• 我是li
        
• 我是li
        
• 我是li
    

    <script> var ul = document.querySelector(&#39;ul&#39;); // 1.不管是文本节点还是元素节点 console.log(ul.firstChild); console.log(ul.lastChild); // 2.返回对应的自元素节点，IE9以上才支持 console.log(ul.firstElementChild); console.log(ul.lastElementChild); // 3.不存在兼容性问题 console.log(ul.children[0]); console.log(ul.children[ul.children.length - 1]); </script>

4.兄弟节点

1.node. nextSibling
nextSibling 返回当前元素的下一个兄弟节点，找不到则返回 null 。同样，也是包含所有的节点。
2.node. previousSibling
previousSibling 返回当前元素上一个兄弟节点，找不到则返回null。同样，也包含所有的节点。
3.node. nextElementSibling
nextElementSibling 返回当前元素下一个兄弟元素节点，找不到返回 null 。
4.node. previousElementSibling
previousElementSibling 返回当前元素上一个兄弟元素节点，找不则返回 null 。
注意：这两个方法有兼容性问题，IE9以上才支持。

那么如何封装一个满足兼容性，又可以找到兄弟元素节点的函数呢

   function getNextElementSibling(element){
       var el = element;
       while(el = el.nextSibling){
           if(el.nodeType == 1){
               return el;
           }
       }
       return null;
   }

上面这段封装的代码就可解决，但不必考虑太多，因为ie浏览器即将要停止服务了，所以你只要记住node. nextElementSibling 这个就行，不必担心兼容性问题。

创建节点

document.createElement (’ tagName ＇)

document.createElenent (）方法创建由 tagName 指定的Н TML 元素。因为这些元素原先不存在，是根据我的需求动态生成的，所以我们也称为动态创建元素节点。

添加节点与添加节点

1.node. appendChild(child)

node.appendChild (）方法将一个节点添加到指定父节点的子节点列表末尾。类似 css 里面的 after 伪元素。

2.node.insertBefore(child,指定元素)

    <script> var ul = document.querySelector("ul"); var li =document.createElement("li"); var span = document.createElement("span") ul.appendChild(li); ul.insertBefore(span,ul.children[0]); </script>

删除节点

node.removeChild(child)

node.removeChild(child) 方法从DOM中删除一个子节点，返回删除的节点。

        
• aniu
        
• marry
        
• tom
    

    <script> var ul = document.querySelector("ul"); ul.removeChild(ul.children[2]); </script>

复制节点（克隆节点）

node.cloneNode ()

node.cloneNode ()方法返回调用该方法的节点的一个副本。也称为克隆节点／拷贝节点
1．如果括号参数为空或者为 false ，则是浅拷贝，即只克隆复制节点本身，不克降里面的子节点。
2．如果括号参数为 true ，则是深度拷贝，会复制节点本身以及里面所有的子节点。

        
• aniu
        
• marry
        
• tom
    

    <script> var ul = document.querySelector("ul"); var li1 = ul.children[0].cloneNode(); //浅拷贝 var li2 = ul.children[0].cloneNode(true); //深拷贝 ul.appendChild(li1); ul.appendChild(li2); </script>

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