2023-08-16T06:21:22.png

<!DOCTYPE html>
<html lang="zh">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>网页名称</title>
  <style>


  </style>
</head>
<body>
  

  <h1 class="www">标题1</h1>
  
  <h1>标题2</h1>

  <h1 id="bt3">标题3</h1>
  
  <form name="ne"></form>
  
  <p class="nav">nav1</p>

<p class="nav">nav2</p>

  <script>
  
  
  //标签名获取元素
  var h1 = document.getElementsByTagName("h1")[1];

  console.log(h1);


  h1.innerHTML = "通过获取标签名更改内容";



  //类名获取元素
  var www = document.getElementsByClassName("www")[0];

  www.innerHTML = "通过获取类名更改内容";




//name获取元素

var ne = document.getElementsByName("ne");


console.log(ne);





//id名获取元素
var bt3 = document.getElementById("bt3");

bt3.innerHTML = "通过获取Id名更改内容";





//css选择器获取元素，单个
var nav = document.querySelector(".nav");

console.log(nav);


//css选择器获取元素，全部
var nav1 = document.querySelectorAll(".nav");

console.log(nav1);


//css选择器获取元素，第几个
var nav2 = document.querySelectorAll(".nav")[1];

console.log(nav2);


  



  </script>
</body>
</html>