lovecoding
/
web0715


			
				
					
						
						
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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: 300px;
            height: 300px;
            box-shadow: 0 0 10px rgba(0,0,0.5);
            background-color: #aaa;
            border-radius: 10px;
            position: fixed;
            top:50%;
            left: 50%;
            margin-left:-150px;
            margin-top: -150px;
            text-align: center;
        }
        .btn{
            width: 100px;
            height: 40px;
            line-height: 40px;
            margin:0 auto;
            border:1px solid #666;
            cursor: pointer;
        }
        .box h1{
            margin-top: 100px;
        }
    </style>
</head>
<body>
    <div class="box">
        <h1>100</h1>
        <div class="btn">开始</div>
    </div>

    <script>
        var oH1 = document.getElementsByTagName("h1")[0];
        var oBtn = document.getElementsByClassName("btn")[0];
        
        oBtn.onclick = function(){
            console.log("本次timer:"+timer);
            var timer = setInterval(function(){
                console.log(timer);
                oH1.innerText--
            },1000)
        }
    </script>
</body>
</html>