JavaScript-leaning/timer1.html at master · LaderBen/JavaScript-leaning · GitHub

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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>
    <script>
        window.onload=function () {
            var oBtnOn= document.getElementById('btnOn');
            var oBtnOff = document.getElementById('btnOff');
            //申明变量timer，用于存储定时器
            var timer=null;

            oBtnOn.onclick=function () {
                timer=setInterval(function(){
                    alert('a');
                },5000);
            };

            oBtnOff.onclick = function () {
                //关闭定时器
                clearInterval(timer);
                alert('定时器已关闭');
            };
        };
    </script>
</head>

<body>
    <input id="btnOn" type="button" value="开启" />
    <input id="btnOff" type="button" value="关闭" />
</body>

</html>