lovecoding
/
Web1020


			
				
					
						
						
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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{
            height: 1000px;
            width: 500px;
            border:4px dashed red;
        }
        .btn{
            position: fixed;
            right: 0;
            bottom: 0;
            font-size: 40px;
            font-weight: bolder;
        }
    </style>
</head>
<body>
    <!-- relative  absolute fixed-->
    <div class="box"></div>
    <div class="btn"> 返回顶部 </div>
    <script>
        var oBtn = document.getElementsByClassName("btn")[0];
        // oBtn = oBtn[0];
        console.log(oBtn);
        oBtn.onclick = function(){
            window.scrollTo(0,0);
        }
    </script>
</body>
</html>