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A detailed explanation of DOM node navigation in JavaScript

藏色散人

Aug 06, 2022 pm 04:49 PM

javascript dom node navigation

This article mainly introduces how to use DOM nodes to obtain page elements. Everything in the page document is a node: including element nodes, text nodes, attribute nodes, document nodes, and comment nodes. The following introduces two major methods of obtaining nodes:

(1) Obtaining nodes (including all nodes such as text nodes, element nodes, etc.)

1.parentNode: Get the parent node

2.childNodes: Get the child nodes, get each child node through the index value

3.firstChild: Get the first child node of the parent node

4.lastChild: Get the last child node of the parent node

5.nextSibling: Get the next sibling node adjacent to the child node

6.previousSibling: Get the adjacent child node The previous sibling node

7.attributes: Get the attribute node

<!DOCTYPE html>
<html>
 
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>由节点关系获取元素</title>
    <style>
 
    </style>
</head>
 
<body>
    <div name="div1">
        <p name=&#39;p1&#39;>文本节点</p>
        <p>2</p>
        <ul>
            <li>3</li>
            <li id="li4">4</li>
            <li>5</li>
            <li>6</li>
        </ul>
    </div>
    <section>7</section>
    <main><span>8</span><i>9</i></main>
    <script>
        //注意换行和空格也属于结点，属于文本节点，按节点关系访问时需要考虑。属性节点无须考虑。
        //1. parentNode获取div
        console.log(document.querySelector(&#39;p&#39;).parentNode);
        console.log(document.querySelector(&#39;p&#39;).parentNode.attributes[0]);
        console.log(document.querySelector(&#39;p&#39;).parentNode.nodeName); //DIV
        console.log(document.querySelector(&#39;p&#39;).parentNode.nodeValue); //null
        console.log(document.querySelector(&#39;p&#39;).parentNode.nodeType); //1 元素节点
        // 2.通过childNodes获取第一个p
        console.log(document.querySelector(&#39;div&#39;).childNodes[1]);
        console.log(document.querySelector(&#39;div&#39;).childNodes[1].firstChild.nodeName);
        console.log(document.querySelector(&#39;div&#39;).childNodes[1].firstChild.nodeType); //2 文本节点
        console.log(document.querySelector(&#39;div&#39;).childNodes[1].firstChild.nodeValue);
        // 3.firstChild获取main中的第一个子节点
        console.log(document.querySelector(&#39;main&#39;).firstChild);
        // 4.lastChild获取main中的最后一个子节点
        console.log(document.querySelector(&#39;main&#39;).lastChild);
        // 5.nextSibling获取相邻下一个兄弟元素
        console.log(document.querySelector(&#39;#li4&#39;).nextSibling.nextSibling);
        // 6.previousSibling获取相邻上一个兄弟元素
        console.log(document.querySelector(&#39;#li4&#39;).previousSibling.previousSibling);
        // 总结：除parentNode外，其他方法谨慎选择，一旦代码格式有变，就会出现错误
        // 通过nodeName获取节点名称
        //通过nodeValue获取节点值
        // 通过nodeType返回节点类型
    </script>
</body>
 
</html>

(2) Get the element node

1.parentElement: Get the parent element Node

2.children: Get the child element node, get each child element node through the index value

3.firstElementChild: Get the first child element node of the parent

4.lastElementChild: Get the last child element node of the parent

5.nextElementSibling: Get the adjacent next sibling element node

6.previousElementSibling: Get the adjacent previous sibling element Node

<!DOCTYPE html>
<html>
 
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>获取子元素节点</title>
</head>
 
<body>
    <div>
        <p>123</p>
        <p>456</p>
        <p>789</p>
    </div>
    <script>
        //p标签总体算一个节点，内部的“123”不算
        console.log(document.querySelector(&#39;div&#39;).childNodes);
        console.log(document.querySelector(&#39;div&#39;).childNodes.length);
        // 获取子元素节点
        console.log(document.querySelector(&#39;div&#39;).children);
        console.log(document.querySelector(&#39;div&#39;).children[1]);
        console.log(document.querySelector(&#39;div&#39;).firstElementChild);
        console.log(document.querySelector(&#39;div&#39;).firstElementChild.nextElementSibling);
        console.log(document.querySelector(&#39;div&#39;).lastElementChild);
        console.log(document.querySelector(&#39;div&#39;).lastElementChild.previousElementSibling);
        console.log(document.querySelector(&#39;div&#39;).children[1].parentElement);
    </script>
</body>
 
</html>

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