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{
            width: 400px;
            height: 400px;
            background-color: #999;
            overflow: hidden;
            position: absolute;
            left: 50%;
            top:50%;
            margin-top: -200px;
            margin-left: -200px;
        }
        .box .num{
            font-size: 50px;
            font-weight: bolder;
            text-align: center;
            margin-top: 100px;
        }
        .box .btn{
            width: 100px;
            height: 50px;
            border:1px solid black;
            text-align: center;
            line-height: 50px;
            margin: 0 auto;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="num">100</div>
        <div class="btn">开始</div>
    </div>
    <script>
        var oNum = document.getElementsByClassName('num')[0];
        var oBtn = document.getElementsByClassName('btn')[0];

        // 存储当前状态 true 代表暂停状态  false 代表运行状态
        var flag = true;
        var timer = 0;
        oBtn.onclick = function(){
            if(true){
                flag = false;
                oBtn.innerText = '暂停';
                timer = setInterval(function(){
                    oNum.innerText --;
                },1000);
            }else{
                // 更正状态值 
                flag = true;
                oBtn.innerText = '开始';
                clearInterval(timer);
            }
        }
    </script>
</body>
</html>