lovecoding
/
W250913


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 100px;
            height: 100px;
            background-color: red;
        }
    </style>
</head>
<body>
    <button>按钮</button>
    <div class="box"></div>
    <script>
        var oBox = document.getElementsByClassName("box");
        var oBtn = document.getElementsByTagName("button");

        // style 控制元素的样式 style 后边跟着的是具体的样式名称 
        // 样式名称如果是复合命名(多个单词构成 background-color) 则需要将中间的-去掉 并将后边的首字母大写(backgroundColor)
        oBtn[0].onclick = function(){
            var num = 200;
            oBox[0].style.width = num + "px";
            oBox[0].style.height = "200px";
            oBox[0].style.backgroundColor = "green";
        }
    </script>
</body>
</html>