一个简单的 JavaScript 倒计时器的代码？

Question

我想使用一个简单的倒计时器，从函数运行时的 30 秒开始，到 0 结束。没有毫秒。 如何对其进行编码？

Answer 1

基于@Layton Everson 提出的解决方案，我开发了一个包括小时、分钟和秒的计数器：

var initialSecs = 86400;
var currentSecs = initialSecs;

setTimeout(decrement,1000); 

function decrement() {
   var displayedSecs = currentSecs % 60;
   var displayedMin = Math.floor(currentSecs / 60) % 60;
   var displayedHrs = Math.floor(currentSecs / 60 /60);

    if(displayedMin <= 9) displayedMin = "0" + displayedMin;
    if(displayedSecs <= 9) displayedSecs = "0" + displayedSecs;
    currentSecs--;
    document.getElementById("timerText").innerHTML = displayedHrs + ":" + displayedMin + ":" + displayedSecs;
    if(currentSecs !== -1) setTimeout(decrement,1000);
}

Answer 2

// Javascript Countdown
// Version 1.01 6/7/07 (1/20/2000)
// by TDavid at http://www.tdscripts.com/
var now = new Date();
var theevent = new Date("Nov 13 2017 22:05:01");
var seconds = (theevent - now) / 1000;
var minutes = seconds / 60;
var hours = minutes / 60;
var days = hours / 24;
ID = window.setTimeout("update();", 1000);

function update() {
  now = new Date();
  seconds = (theevent - now) / 1000;
  seconds = Math.round(seconds);
  minutes = seconds / 60;
  minutes = Math.round(minutes);
  hours = minutes / 60;
  hours = Math.round(hours);
  days = hours / 24;
  days = Math.round(days);
  document.form1.days.value = days;
  document.form1.hours.value = hours;
  document.form1.minutes.value = minutes;
  document.form1.seconds.value = seconds;
  ID = window.setTimeout("update();", 1000);
}

<p><font face="Arial" size="3">Countdown To January 31, 2000, at 12:00: </font>
</p>
<form name="form1">
  <p>Days
    <input type="text" name="days" value="0" size="3">Hours
    <input type="text" name="hours" value="0" size="4">Minutes
    <input type="text" name="minutes" value="0" size="7">Seconds
    <input type="text" name="seconds" value="0" size="7">
  </p>
</form>

Answer 3

我的解决方案适用于 MySQL 日期时间格式并提供回调函数。 关于完成。
免责声明：仅适用于分钟和秒，因为这是我需要的。

jQuery.fn.countDownTimer = function(futureDate, callback){
    if(!futureDate){
        throw 'Invalid date!';
    }

    var currentTs = +new Date();
    var futureDateTs = +new Date(futureDate);

    if(futureDateTs <= currentTs){
        throw 'Invalid date!';
    }


    var diff = Math.round((futureDateTs - currentTs) / 1000);
    var that = this;

    (function countdownLoop(){
        // Get hours/minutes from timestamp
        var m = Math.floor(diff % 3600 / 60);
        var s = Math.floor(diff % 3600 % 60);
        var text = zeroPad(m, 2) + ':' + zeroPad(s, 2);

        $(that).text(text);

        if(diff <= 0){
            typeof callback === 'function' ? callback.call(that) : void(0);
            return;
        }

        diff--;
        setTimeout(countdownLoop, 1000);
    })();

    function zeroPad(num, places) {
      var zero = places - num.toString().length + 1;
      return Array(+(zero > 0 && zero)).join("0") + num;
    }
}

// $('.heading').countDownTimer('2018-04-02 16:00:59', function(){ // on complete})

Answer 4

var hr = 0;
var min = 0;
var sec = 0;
var count = 0;
var flag = false;


function start(){
    flag = true;
    stopwatch();


}
function stop(){
    flag = false;

}

function reset(){
    flag = false;
    hr = 0;
    min = 0;
    sec = 0;
    count = 0;
    document.getElementById("hr").innerHTML = "00";
    document.getElementById("min").innerHTML = "00";
    document.getElementById("sec").innerHTML = "00";
    document.getElementById("count").innerHTML = "00";

}



function stopwatch(){
    if(flag == true){
        count = count + 1;
        setTimeout( 'stopwatch()', 10);

    if(count ==100){
        count =0;
        sec = sec +1;

    }
    }

    if(sec ==60){
        min = min +1 ;
        sec = 0;

    }
      if(min == 60){
        hr = hr +1 ;
        min = 0;
        sec = 0;

    }
    var hrs = hr;
    var mins = min;
    var secs = sec;
    if(hr<10){
        hrs ="0" + hr; 

    }
    if(min<10){
        mins ="0" + min; 

    }
   if(sec<10){
        secs ="0" + sec; 

    }
    document.getElementById("hr").innerHTML = hrs;
    document.getElementById("min").innerHTML = mins;
    document.getElementById("sec").innerHTML = secs;
    document.getElementById("count").innerHTML = count;
      
}

Answer 5

var count=30;

var counter=setInterval(timer, 1000); //1000 will  run it every 1 second

function timer()
{
  count=count-1;
  if (count <= 0)
  {
     clearInterval(counter);
     //counter ended, do something here
     return;
  }

  //Do code for showing the number of seconds here
}

要使计时器的代码出现在段落中（或页面上的任何其他位置），只需将行：

<span id="timer"></span>

放在您希望秒数出现的位置即可。 然后在您的 timer() 函数中插入以下行，如下所示：

function timer()
{
  count=count-1;
  if (count <= 0)
  {
     clearInterval(counter);
     return;
  }

 document.getElementById("timer").innerHTML=count + " secs"; // watch for spelling
}

Answer 6

我前段时间写了这个脚本：

用法：

var myCounter = new Countdown({  
    seconds:5,  // number of seconds to count down
    onUpdateStatus: function(sec){console.log(sec);}, // callback for each second
    onCounterEnd: function(){ alert('counter ended!');} // final action
});

myCounter.start();

---

function Countdown(options) {
  var timer,
  instance = this,
  seconds = options.seconds || 10,
  updateStatus = options.onUpdateStatus || function () {},
  counterEnd = options.onCounterEnd || function () {};

  function decrementCounter() {
    updateStatus(seconds);
    if (seconds === 0) {
      counterEnd();
      instance.stop();
    }
    seconds--;
  }

  this.start = function () {
    clearInterval(timer);
    timer = 0;
    seconds = options.seconds;
    timer = setInterval(decrementCounter, 1000);
  };

  this.stop = function () {
    clearInterval(timer);
  };
}

Answer 7

到目前为止，答案似乎依赖于立即运行的代码。 如果你设置一个1000ms的定时器，它实际上会在1008左右。

您应该这样做：

function timer(time,update,complete) {
    var start = new Date().getTime();
    var interval = setInterval(function() {
        var now = time-(new Date().getTime()-start);
        if( now <= 0) {
            clearInterval(interval);
            complete();
        }
        else update(Math.floor(now/1000));
    },100); // the smaller this number, the more accurate the timer will be
}

要使用，请致电：

timer(
    5000, // milliseconds
    function(timeleft) { // called every step to update the visible countdown
        document.getElementById('timer').innerHTML = timeleft+" second(s)";
    },
    function() { // what to do after
        alert("Timer complete!");
    }
);

Answer 8

如果有人需要几分钟和几秒钟的话，这是另一个：

    var mins = 10;  //Set the number of minutes you need
    var secs = mins * 60;
    var currentSeconds = 0;
    var currentMinutes = 0;
    /* 
     * The following line has been commented out due to a suggestion left in the comments. The line below it has not been tested. 
     * setTimeout('Decrement()',1000);
     */
    setTimeout(Decrement,1000); 

    function Decrement() {
        currentMinutes = Math.floor(secs / 60);
        currentSeconds = secs % 60;
        if(currentSeconds <= 9) currentSeconds = "0" + currentSeconds;
        secs--;
        document.getElementById("timerText").innerHTML = currentMinutes + ":" + currentSeconds; //Set the element id you need the time put into.
        if(secs !== -1) setTimeout('Decrement()',1000);
    }

Answer 9

// Javascript Countdown
// Version 1.01 6/7/07 (1/20/2000)
// by TDavid at http://www.tdscripts.com/
var now = new Date();
var theevent = new Date("Sep 29 2007 00:00:01");
var seconds = (theevent - now) / 1000;
var minutes = seconds / 60;
var hours = minutes / 60;
var days = hours / 24;
ID = window.setTimeout("update();", 1000);

function update() {
  now = new Date();
  seconds = (theevent - now) / 1000;
  seconds = Math.round(seconds);
  minutes = seconds / 60;
  minutes = Math.round(minutes);
  hours = minutes / 60;
  hours = Math.round(hours);
  days = hours / 24;
  days = Math.round(days);
  document.form1.days.value = days;
  document.form1.hours.value = hours;
  document.form1.minutes.value = minutes;
  document.form1.seconds.value = seconds;
  ID = window.setTimeout("update();", 1000);
}

<p><font face="Arial" size="3">Countdown To January 31, 2000, at 12:00: </font>
</p>
<form name="form1">
  <p>Days
    <input type="text" name="days" value="0" size="3">Hours
    <input type="text" name="hours" value="0" size="4">Minutes
    <input type="text" name="minutes" value="0" size="7">Seconds
    <input type="text" name="seconds" value="0" size="7">
  </p>
</form>

Answer 10

刚刚修改了@ClickUpvote的答案：

您可以使用IIFE（立即调用函数表达式） 和递归使其更容易一些：

var i = 5;  //set the countdown
(function timer(){
    if (--i < 0) return;
    setTimeout(function(){
        console.log(i + ' secs');  //do stuff here
        timer();
    }, 1000);
})();

var i = 5;
(function timer(){
    if (--i < 0) return;
    setTimeout(function(){
        document.getElementsByTagName('h1')[0].innerHTML = i + ' secs';
        timer();
    }, 1000);
})();

<h1>5 secs</h1>

Answer 11

扩展已接受的答案，您的机器将进入睡眠状态等可能会延迟计时器的工作。 您可以获得真实的时间，但需要进行一些处理。 这将给出真实的剩余时间。

<span id="timer"></span>

<script>
var now = new Date();
var timeup = now.setSeconds(now.getSeconds() + 30);
//var timeup = now.setHours(now.getHours() + 1);

var counter = setInterval(timer, 1000);

function timer() {
  now = new Date();
  count = Math.round((timeup - now)/1000);
  if (now > timeup) {
      window.location = "/logout"; //or somethin'
      clearInterval(counter);
      return;
  }
  var seconds = Math.floor((count%60));
  var minutes = Math.floor((count/60) % 60);
  document.getElementById("timer").innerHTML = minutes + ":" + seconds;
}
</script>

Answer 12

为了性能，我们现在可以安全地使用 requestAnimationFrame 用于快速循环，而不是 setInterval/setTimeout。

使用 setInterval/setTimeout 时，如果循环任务花费的时间超过间隔时间，浏览器将简单地延长间隔循环，以继续完整渲染。 这正在造成问题。 setInterval/setTimeout 过载几分钟后，这可能会冻结选项卡、浏览器或整个计算机。

互联网设备的性能多种多样，因此很难以毫秒为单位硬编码固定的间隔时间！

使用日期对象来比较开始日期纪元和当前。 这比其他一切都快得多，浏览器将以稳定的 60FPS 处理一切（1000 / 60 = 每帧 16.66 毫秒） -眨眼四分之一次 - 如果任务在循环中如果需要更多，浏览器将放弃一些重绘。

这在我们的眼睛注意到之前留出了余量（人类 = 24FPS => 1000 / 24 = 41.66 毫秒每帧 = 流畅的动画！）

https://caniuse.com/#search=requestAnimationFrame

/* Seconds to (STRING)HH:MM:SS.MS ------------------------*/
/* This time format is compatible with FFMPEG ------------*/
function secToTimer(sec){
  const o = new Date(0), p =  new Date(sec * 1000)
  return new Date(p.getTime()-o.getTime()).toString().split(" ")[4] + "." + p.getMilliseconds()
}

/* Countdown loop ----------------------------------------*/
let job, origin = new Date().getTime()
const timer = () => {
  job = requestAnimationFrame(timer)
  OUT.textContent = secToTimer((new Date().getTime() - origin) / 1000)
}

/* Start looping -----------------------------------------*/
requestAnimationFrame(timer)

/* Stop looping ------------------------------------------*/
// cancelAnimationFrame(job)

/* Reset the start date ----------------------------------*/
// origin = new Date().getTime()

span {font-size:4rem}

<span id="OUT"></span>
<br>
<button onclick="origin = new Date().getTime()">RESET</button>
<button onclick="requestAnimationFrame(timer)">RESTART</button>
<button onclick="cancelAnimationFrame(job)">STOP</button>

Answer 13

使用纯JS可以进行如下操作。 您只需向该函数提供秒数，它就会完成其余的工作。

var insertZero = n => n < 10 ? "0"+n : ""+n,
   displayTime = n => n ? time.textContent = insertZero(~~(n/3600)%3600) + ":" +
                                             insertZero(~~(n/60)%60) + ":" +
                                             insertZero(n%60)
                        : time.textContent = "IGNITION..!",
 countDownFrom = n => (displayTime(n), setTimeout(_ => n ? sid = countDownFrom(--n)
                                                         : displayTime(n), 1000)),
           sid;
countDownFrom(3610);
setTimeout(_ => clearTimeout(sid),20005);

<div id="time"></div>