lovecoding
/
VIP20


			
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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>
  <div id="div1">111111111111111</div>
  <p id="p1">222222222222</p>
  <h1>hahahhahhhaahhahahh</h1>
  <ul id="ul1">
    <li>1</li>
    <li>2</li>
    <li>3</li>
  </ul>
  <script>
    var div1 = document.getElementById('div1')
    var p1 = document.getElementById('p1')
    var ul1 = document.getElementById('ul1')
    // console.log(div1.nodeType)
    // console.log(p1.nodeName)
    // console.log(div1.nextElementSibling)
    // console.log(div1.nextSibling)
    // console.log(div1.previousSibling)
    // console.log(div1.previousElementSibling)
    //nextSibling 指向下一个兄弟节点 
    //nextElementSibling 指向下一个元素节点
    //previousSibling 指向上一个兄弟节点
    //previousElementSibling 指向上一个元素节点  如果这个节点就是第一个元素节点  那么该值为null
    console.log(p1.nextElementSibling)
    
    //firstChild  指向在childNodes列表中的第一个节点
    console.log(ul1.firstChild)
    console.log(ul1.lastChild)


    function next(elem){
      do{
        elem = elem.nextSibling
      }while(elem.nodeType != 1)
      return elem
    }
    console.log(next(div1))


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