lovecoding
/
Web1020


			
				
					
						
						
							12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758
							<!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;
            border-radius: 10px;
            font-size: 50px;
            text-align: center;
            line-height: 400px;
            position: absolute;
            left: 50%;
            top: 50%;
            margin-left: -200px;
            margin-top: -200px;
        }
    </style>
</head>
<body>
    <div class="box">10</div>
    <script>
        // 获取元素
        var oBox = document.getElementsByClassName("box");
        // 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
        oBox = oBox[0];
        // console.log(oBox)
        // oBox.innerText = 9;

        // 倒计时方法一
        // var num = 10;
        // var timer = setInterval(function(){
        //     if(num == 0){
        //         clearInterval(timer);
        //     }else{
        //         num--;
        //         console.log(num)
        //         oBox.innerText = num;
        //     }
        // },1000);

        // 倒计时方法二
        var timer = setInterval(function(){
            //oBox.innerText 获取到的值是字符串型
            if(oBox.innerText == 0){
                clearInterval(timer);
            }else{
                oBox.innerText = oBox.innerText - 1;
            }
        },1000);

    </script>
</body>
</html>