如何在JavaScript中编写倒计时定时器？
如何在JavaScript中编写倒计时定时器？
提问于 2013-12-17 02:41:08
只是想问一下如何创建最简单的倒计时计时器。
网站上会有这样一句话：
“注册将在05:00分钟后关闭！”
所以，我想要做的是创建一个简单的js倒计时计时器，它从"05:00“到"00:00”，一旦结束就重置为"05:00“。
我之前看过一些答案，但它们看起来都太紧张了(Date对象等)。为了我想做的事。
回答 3
Stack Overflow用户
回答已采纳
发布于 2013-12-17 02:50:20
我有两个演示，一个有jQuery，另一个没有。这两种方法都不使用日期函数，也不是最简单的。
function startTimer(duration, display) {
var timer = duration, minutes, seconds;
setInterval(function () {
minutes = parseInt(timer / 60, 10);
seconds = parseInt(timer % 60, 10);
minutes = minutes < 10 ? "0" + minutes : minutes;
seconds = seconds < 10 ? "0" + seconds : seconds;
display.textContent = minutes + ":" + seconds;
if (--timer < 0) {
timer = duration;
}
}, 1000);
}
window.onload = function () {
var fiveMinutes = 60 * 5,
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};<body>
<div>Registration closes in <span id="time">05:00</span> minutes!</div>
</body>
function startTimer(duration, display) {
var timer = duration, minutes, seconds;
setInterval(function () {
minutes = parseInt(timer / 60, 10);
seconds = parseInt(timer % 60, 10);
minutes = minutes < 10 ? "0" + minutes : minutes;
seconds = seconds < 10 ? "0" + seconds : seconds;
display.text(minutes + ":" + seconds);
if (--timer < 0) {
timer = duration;
}
}, 1000);
}
jQuery(function ($) {
var fiveMinutes = 60 * 5,
display = $('#time');
startTimer(fiveMinutes, display);
});然而，如果你想要一个更精确的计时器，而且只需要稍微复杂一点：：
function startTimer(duration, display) {
var start = Date.now(),
diff,
minutes,
seconds;
function timer() {
// get the number of seconds that have elapsed since
// startTimer() was called
diff = duration - (((Date.now() - start) / 1000) | 0);
// does the same job as parseInt truncates the float
minutes = (diff / 60) | 0;
seconds = (diff % 60) | 0;
minutes = minutes < 10 ? "0" + minutes : minutes;
seconds = seconds < 10 ? "0" + seconds : seconds;
display.textContent = minutes + ":" + seconds;
if (diff <= 0) {
// add one second so that the count down starts at the full duration
// example 05:00 not 04:59
start = Date.now() + 1000;
}
};
// we don't want to wait a full second before the timer starts
timer();
setInterval(timer, 1000);
}
window.onload = function () {
var fiveMinutes = 60 * 5,
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};<body>
<div>Registration closes in <span id="time"></span> minutes!</div>
</body>
现在我们已经创建了一些非常简单的计时器，我们可以开始考虑可重用性和分离关注点。我们可以通过问“倒计时定时器应该做什么”来做到这一点。
- 倒计时计时器是否应该倒计时？是
- 倒计时计时器是否应该知道如何在DOM上显示自己？No
- 倒计时计时器是否应该知道在达到0时重新启动？否E221
- 倒计时计时器是否应该为客户端提供访问剩余时间的方法？Yes
考虑到这些，让我们编写一个更好(但仍然非常简单)的CountDownTimer
function CountDownTimer(duration, granularity) {
this.duration = duration;
this.granularity = granularity || 1000;
this.tickFtns = [];
this.running = false;
}
CountDownTimer.prototype.start = function() {
if (this.running) {
return;
}
this.running = true;
var start = Date.now(),
that = this,
diff, obj;
(function timer() {
diff = that.duration - (((Date.now() - start) / 1000) | 0);
if (diff > 0) {
setTimeout(timer, that.granularity);
} else {
diff = 0;
that.running = false;
}
obj = CountDownTimer.parse(diff);
that.tickFtns.forEach(function(ftn) {
ftn.call(this, obj.minutes, obj.seconds);
}, that);
}());
};
CountDownTimer.prototype.onTick = function(ftn) {
if (typeof ftn === 'function') {
this.tickFtns.push(ftn);
}
return this;
};
CountDownTimer.prototype.expired = function() {
return !this.running;
};
CountDownTimer.parse = function(seconds) {
return {
'minutes': (seconds / 60) | 0,
'seconds': (seconds % 60) | 0
};
};那么为什么这个实现比其他实现更好呢？这里有一些你可以用它做什么的例子。请注意，除了第一个示例之外，所有示例都不能由startTimer函数实现。
An example that displays the time in XX:XX format and restarts after reaching 00:00
An example that displays the time in two different formats
An example that has two different timers and only one restarts
An example that starts the count down timer when a button is pressed
Stack Overflow用户
发布于 2013-12-17 02:44:57
你可以使用setInterval.Below很容易地创建一个定时器功能，这是你可以用它来创建定时器的代码。
http://jsfiddle.net/ayyadurai/GXzhZ/1/
window.onload = function() {
var minute = 5;
var sec = 60;
setInterval(function() {
document.getElementById("timer").innerHTML = minute + " : " + sec;
sec--;
if (sec == 00) {
minute --;
sec = 60;
if (minute == 0) {
minute = 5;
}
}
}, 1000);
}Registration closes in <span id="timer">05:00<span> minutes!
Stack Overflow用户
发布于 2013-12-17 02:54:55
如果你想要一个真正的计时器，你需要使用date对象。
计算差值。
格式化您的字符串。
window.onload=function(){
var start=Date.now(),r=document.getElementById('r');
(function f(){
var diff=Date.now()-start,ns=(((3e5-diff)/1e3)>>0),m=(ns/60)>>0,s=ns-m*60;
r.textContent="Registration closes in "+m+':'+((''+s).length>1?'':'0')+s;
if(diff>3e5){
start=Date.now()
}
setTimeout(f,1e3);
})();
}示例
计时器不是很精确
var time=5*60,r=document.getElementById('r'),tmp=time;
setInterval(function(){
var c=tmp--,m=(c/60)>>0,s=(c-m*60)+'';
r.textContent='Registration closes in '+m+':'+(s.length>1?'':'0')+s
tmp!=0||(tmp=time);
},1000);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/20618355
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