<!doctype html>
<html lang="en">
<head>
???<meta charset="UTF-8">
???<meta name="viewport"
?????????content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
???<meta http-equiv="X-UA-Compatible" content="ie=edge">
???<title>Document</title>
</head>
<body>
<div>当前时间为:<span id="timeNow">00:00:00</span></div>
<button id="timeBegin">计时开始</button>
<button id="timeEnd">计时结束</button>
<button id="timeClear">计时清除</button>
<script>
???//定义初始值 计时器
???var timer = "";
???//开始计时
???var beginBtn = document.getElementById("timeBegin");
???var endBtn = document.getElementById("timeEnd");
???var clearBtn = document.getElementById("timeClear");
???var min,second,millisecond;//分 ?秒 ?毫秒
???min= second=millisecond=0; //初始化
???function time() {
???????millisecond+=50;
???????if (millisecond >= 1000) {
???????????millisecond=0
???????????second += 1;
???????}
???????if (second >= 60) {
???????????second=0
???????????min += 1;
???????}
???????counts = min + ‘:‘ + second + ‘:‘ + millisecond;
???????document.getElementById("timeNow").innerText = counts;
???}
???//开始计时
???function BeginTime() {
???????beginBtn.onclick = function () {
???????????timer = setInterval(time, 50);
???????}
???}
???//结束计时
???function EndTime() {
???????endBtn.onclick = function () {
???????????clearInterval(timer);
???????}
???}
???//计时清除
???function ClearTime() {
???????clearBtn.onclick = function () {
???????????document.getElementById("timeNow").innerHTML = "00:00:00";
???????}
???}
???BeginTime();
???EndTime();
???ClearTime()
</script>
</body>
</html>
JS计时器
原文地址：https://www.cnblogs.com/shenbo666/p/9522578.html