15.setInterval

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>T2-setInterval</title>
</head>
<body>
<p id="p"></p>
<script>
    var n = 1000;
    var show = function () {

        document.getElementById("p").innerHTML = "倒计时：" + (n--);
    };
    setInterval(show,1000);

</script>
</body>
</html>
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原文地址：https://www.cnblogs.com/mx2036/p/6704956.html