lovecoding
/
VIP22


			
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							<!DOCTYPE html>
<html lang="en">
<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>Document</title>
</head>
<body> 
  <p id="p1">22222</p>
  <div id="div1">11111</div>
  <h2>hhhhhhhh</h2>
  <ul id="ul1">
    <li>1</li>
    <li>2</li>
    <li>3</li>
  </ul>
  <script>
    var p1 = document.getElementById('p1')
    var ul1 = document.getElementById('ul1')
    console.log(p1.nodeName)
    // console.log(p1.nextSibling)
    // console.log(p1.previousSibling)
    //nextSibling  指向后一个兄弟节点   如果这个节点就是最后一个兄弟节点  那么该值为null
    //previousSibling 指向前一个兄弟节点   如果这个节点就是第一个兄弟节点  那么该值为null
    // nextElementSibling 指向以一个元素节点
    // previousElementSibling 指向上一个元素节点
    console.log(p1.nextElementSibling)
    console.log(p1.previousElementSibling)


    function next(elem){
      do{
        elem = elem.nextSibling
      }while(elem.nodeType != 1)
      return elem
    }
    console.log(next(p1))

    //在列表里面第一个节点
    console.log(ul1.firstChild)
    console.log(ul1.lastChild)
    console.log(ul1.firstElementChild)
    console.log(ul1.lastElementChild)

    function first(elem){
      elem = elem.firstChild
      if(elem.nodeType != 1){
        elem = next(elem)
      }
      return elem
    }
    console.log(first(ul1))
  </script>
</body>
</html>