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@@ -0,0 +1,58 @@
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+<!DOCTYPE html>
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+<html lang="en">
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+<head>
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+ <meta charset="UTF-8">
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+ <meta name="viewport" content="width=device-width, initial-scale=1.0">
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+ <title>Document</title>
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+ <style>
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+ .box{
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+ width: 400px;
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+ height: 400px;
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+ background-color: #999;
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+ border-radius: 10px;
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+ font-size: 50px;
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+ text-align: center;
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+ line-height: 400px;
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+ position: absolute;
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+ left: 50%;
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+ top: 50%;
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+ margin-left: -200px;
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+ margin-top: -200px;
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+ }
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+ </style>
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+</head>
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+<body>
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+ <div class="box">10</div>
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+ <script>
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+ // 获取元素
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+ var oBox = document.getElementsByClassName("box");
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+ // 获取到的内容是多个元素还是一个 如果是个容器那么我们需要将要控制的元素取出来
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+ oBox = oBox[0];
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+ // console.log(oBox)
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+ // oBox.innerText = 9;
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+
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+ // 倒计时方法一
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+ // var num = 10;
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+ // var timer = setInterval(function(){
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+ // if(num == 0){
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+ // clearInterval(timer);
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+ // }else{
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+ // num--;
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+ // console.log(num)
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+ // oBox.innerText = num;
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+ // }
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+ // },1000);
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+
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+ // 倒计时方法二
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+ var timer = setInterval(function(){
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+ //oBox.innerText 获取到的值是字符串型
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+ if(oBox.innerText == 0){
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+ clearInterval(timer);
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+ }else{
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+ oBox.innerText = oBox.innerText - 1;
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+ }
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+ },1000);
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+
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+ </script>
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+</body>
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+</html>
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