HTML css/style/关键字位置不同

<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box{
      background-color:red;     
            width: 100px;
            height: 100px;
            margin-top: 35px;
        }
    </style>
</head>
<body>
<div class="box"  >
</div>
<script>
    var box=document.getElementsByClassName("box")[0];
    box.onclick=function() {
    box.style.backgroundColor = "blue";
    }
</script>
</body>
</html>

两边的backgroundcolor 关键字名字不同

body style 里的写法

<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div style=" 100px; height: 100px;background-color:pink;">
</div>
    <script>
      var div= document.getElementsByTagName("div")[0];
      div.onmouseover=function(){
          div.style.width="200px";
          div.style.height="200px";
          div.style.backgroundColor="black";
          div.style.opacity="0.2";
          div.style.filter="alpha(opacity=20)";
      }
    </script>
</body>
</html>