<SCRIPT LANGUAGE="JavaScript"> <!-- var maxtime = 60*60 //一个小时，按秒计算，自己调整! function CountDown(){ if(maxtime>=0){ minutes = Math.floor(maxtime/60); seconds = Math.floor(maxtime%60); msg = "距离结束还有"+minutes+"分"+seconds+"秒"; document.all["timer"].innerHTML=msg; if(maxtime == 5*60) alert('注意，还有5分钟!'); --maxtime; } else{ clearInterval(timer); alert("时间到，结束!"); } } timer = setInterval("CountDown()",1000); //--> </SCRIPT> <div></div>
Javascript倒计时器 - 采用系统时间自校验
这次利用系统时间自校验倒计时, 无需手工调校使得倒计时更为精确, 代码及详细注释如下:
<span>00:01:11:00</span> <input type="button" value="start countdown!"> <input type="button" value="stop countdown!"> <br> <input type="text"> <input type="text"> <script language="Javascript"> var normalelapse = 100; var nextelapse = normalelapse; var counter; var startTime; var start = clock.innerText; var finish = "00:00:00:00"; var timer = null; // 开始运行 function run() { startB.disabled = true; endB.disabled = false; counter = 0; // 初始化开始时间 startTime = new Date().valueOf(); // nextelapse是定时时间, 初始时为100毫秒 // 注意setInterval函数: 时间逝去nextelapse(毫秒)后, onTimer才开始执行 timer = window.setInterval("onTimer()", nextelapse); } // 停止运行 function stop() { startB.disabled = false; endB.disabled = true; window.clearTimeout(timer); } window.onload = function() { endB.disabled = true; }; // 倒计时函数 function onTimer() { if (start == finish) { window.clearInterval(timer); alert("time is up!"); return; } var hms = new String(start).split(":"); var ms = new Number(hms[3]); var s = new Number(hms[2]); var m = new Number(hms[1]); var h = new Number(hms[0]); ms -= 10; if (ms < 0) { ms = 90; s -= 1; if (s < 0) { s = 59; m -= 1; } if (m < 0) { m = 59; h -= 1; } } var ms = ms < 10 ? ("0" + ms) : ms; var ss = s < 10 ? ("0" + s) : s; var sm = m < 10 ? ("0" + m) : m; var sh = h < 10 ? ("0" + h) : h; start = sh + ":" + sm + ":" + ss + ":" + ms; clock.innerText = start; // 清除上一次的定时器 window.clearInterval(timer); // 自校验系统时间得到时间差, 并由此得到下次所启动的新定时器的时间nextelapse counter++; var counterSecs = counter * 100; var elapseSecs = new Date().valueOf() - startTime; var diffSecs = counterSecs - elapseSecs; nextelapse = normalelapse + diffSecs; diff.value = counterSecs + "-" + elapseSecs + "=" + diffSecs; next.value = "nextelapse = " + nextelapse; if (nextelapse < 0) nextelapse = 0; // 启动新的定时器 timer = window.setInterval("onTimer()", nextelapse); } </script>
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