求大神帮我看一下我这代码到底是哪出问题了，怎么也不出效果

 

<!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">
  <link rel="stylesheet" href="./test.css" id="cssFile">
  <title>Document</title>
</head>
<body>
<h3>change Style</h3>
<div onclick="changeStyle('testa')">
  testa
</div>
<div onclick="changeStyle('testb')">
  testB
</div>
<script>
  function changeStyle(type){
    let css = document.getElementById('cssFile')
    css.href = `./${type}.css`
  }
</script>
</body>
</html>

三个css 文件

// test 
html div{
  display: inline-block;
  margin: 20px;
  width: 200px;
  border: 1px solid black;
  color: black;
}

//testa
html div{
  display: inline-block;
  margin: 20px;
  width: 200px;
  border: 1px solid red;
  color: red;
}
//testb
html div{
  display: inline-block;
  margin: 20px;
  width: 200px;
  border: 1px solid blue;
  color: blue;
}

可以的话，点个采纳

这里改一下：css.href = 'css/' + name + '.css'