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Countdown timer is lagging behind

I am trying to create countdown timer between 2 dates but the time is lagging behind after a while.
My PHP backend returns the difference between current time and X time in the future, for example current time and 2 hours in advance. This difference is passed to my HTML frontent in a .countdown class in the following format 03:20:15 which I use a javascript function to countdown the difference. Here is my function:
$(".countdown").each(function() {
var $e = $(this);
var interval = setInterval(function() {
var timer2 = $e.html();
var timer = timer2.split(':');
var hours = parseInt(timer[0], 10);
var minutes = parseInt(timer[1], 10);
var seconds = parseInt(timer[2], 10);
--seconds;
minutes = (seconds < 0) ? --minutes : minutes;
hours = (minutes < 0) ? --hours : hours;
if(hours < 0) {
clearInterval(interval);
window.location.reload();
} else {
seconds = (seconds < 0) ? 59 : seconds;
seconds = (seconds < 10) ? '0' + seconds : seconds;
minutes = (minutes < 0) ? 59 : minutes;
minutes = (minutes < 10) ? '0' + minutes : minutes;
hours = (hours < 10) ? '0' + hours : hours;
$e.html(hours + ':' + minutes + ':' + seconds);
}
}, 1000);
});
The code works as expected but after a few minutes, lets say 2-3 minutes, if you refresh the page or open it in a new window you will see that the countdown timer was lagging behind by seconds/minutes. Does someone know what Im doing wrong?

You should compute the difference between (new Date()) and the target date. Use that difference and format new HTML string instead of parsing it to a hour, minutes, seconds value for decrementing.
details
The setInterval api specs suggest that delays due to CPU load, other tasks, etc, are to be expected.
https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html#timers
Your handler is called at approximately equal intervals while you consider them to be exact. At first iteration the actual time may differ from a planed time by some small amount (let say 4ms). Yet you are changing your counter by 1000 ms. As many more iterations passed this difference accumulates and become noticeable. A few minutes is enough to make this happens.
If you, on the other hand, pre-compute the target date-time value and will use the difference between current time and the target time your code will not be sensible to api inexactness.
$(".countdown").each(function () {
var $e = $(this);
const totalSeconds = (dt) => Math.floor(dt.valueOf() / 1000);
const f1 = (timer2) => {
var timer = timer2.split(':');
var tdt = new Date().setHours(
parseInt(timer[0]) + tdt.getHours(),
parseInt(timer[1]) + tdt.getMinutes(),
parseInt(timer[2]) + tdt.getSeconds());
return totalSeconds(tdt);
};
const targetTime = f1($e.html());
setInterval(function () {
var timeSpan = targetTime - totalSeconds(new Date());
if (timeSpan < 0) {
window.location.reload();
} else {
var seconds = timeSpan % 60;
var totalMinutes = Math.floor(timeSpan / 60);
var minutes = totalMinutes % 60;
var hours = Math.floor(totalMinutes / 60);
$e.html(hours + ':' + minutes + ':' + seconds);;
}
}, 1000);
});
see also:
https://jsfiddle.net/8dygbo9a/1/

jQuery time count

Here's the scenario, I have a time that counts the time_taken by a user. What I want is to get the exact time_taken based from the timer. For example, a user take an exam, then after he/she take the exam, the time_taken will be submitted (e.g. 1hr 25mins 23secs). Please see my code below.
$(document).ready(function(){
var d;
setInterval(function(){
d = new Date();
dates = d.getHours() + ':' + d.getMinutes() + ':' + d.getSeconds();
$('#timeTaken').val(dates);
}, 1000);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" id="timeTaken" value="">

Here is Fiddle for the solution
https://jsfiddle.net/djzsddz6/1/
Ans Solution is below:
$(document).ready(function(){
var seconds = 0, minutes = 0 , hours = 0;
setInterval(function(){
seconds++;
if(seconds == 60){
minutes++
seconds = 0;
}
if(minutes == 60){
hours++
minutes = 0;
}
console.log(hours, minutes, seconds);
$('#timeTaken').val(`${hours}:${minutes}:${seconds}`);
}, 1000);
});

I don't really see the point to use an input there, you can just display in a span and when the form gets submitted take the time elapsed and send it with other data. Anyways, this should work for you:
$(document).ready(function () {
var time_start = new Date();
setInterval(function () {
var time_end = new Date();
var time_diff = (time_end - time_start);
// hours
var hours = Math.floor(time_diff / 1000 / 60 / 60);
// minutes
time_diff = time_diff - hours * 1000 * 60 * 60;
var minutes = Math.floor(time_diff / 1000 / 60);
// seconds
time_diff = time_diff - minutes * 1000 * 60;
var seconds = Math.floor(time_diff / 1000);
renderTime(hours, minutes, seconds);
}, 1000);
});
function renderTime (hrs, min, sec) {
var str = convertTime(hrs) + ":" + convertTime(min) + ":" + convertTime(sec);
$("#timeTaken").val(str);
}
function convertTime (val) {
return val < 10 ? "0" + val : val;
}
What's going on here is we have the time_start which does not change and we have setInterval function that is triggered every second. There we create new Date object, and the subtract the static one from it, which returns the time difference in milliseconds. We do the weird Math.flooring and subtracting, so we can have hours, minutes and seconds as an integers (not floats). Then we use render function to display the time inside an desired element.
Why I think it's a better solution then the others are, is that if you want to handle the user's page refresh you just need to save one variable to cookie or something else and it will work regardless of the page refresh.
Handling the page refresh would look like (with cookie saved for 2 hrs):
function updateTimeCookie () {
var time_now = new Date()
var value = JSON.stringify(time_now);
var expires = time_now.setTime(time_now.getTime() + 7200);
$.cookie("timeStart", value, { expires: expires });
};
// to get Date object from cookie: new Date(JSON.parse($.cookie("timeStart")))
To use $.cookie() you must first include jQuery Cookie Plugin.
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-cookie/1.4.1/jquery.cookie.min.js"></script>
Working fiddle without cookie: https://jsfiddle.net/qc3axmf4/1/
Working fiddle with cookie: https://jsfiddle.net/ta8bnzs0/2/

Rather than getting date at every second you can keep the counter in set interval which will updated at every second. At the time of submission you can perform division and modulus operation to get exact time taken
Example
$(document).ready(function(){
var timer =0;
setInterval(function(){
Timer +=1;
// Code for display in hr mm and ss
$('#timeTaken').val(dates);
}, 1000'
});
You can also convert second in time valueby using moment.js
Hope this helps you.
Happy coding

Problems creating a basic clock with javascript [closed]

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Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 8 years ago.
Improve this question
I'm trying to build just a simple clock using javascript, but I'm at a loss at to why it isn't working.
$(document).ready(function() {
function updateTime() {
var now = newDate();
var hours = now.getHours();
var minutes = now.getMinutes();
var seconds = now.getSeconds();
var currenTime = hours + ':' + minutes ':' + seconds;
var counter = document.getElementById('counter');
counter.innerHTML = currentTime;
}
updateTime();
});

First you need to fix bugs in your code:
space between new and Date (new Date).
typo in var currenTime -> var currentTime
missing +after minutes in var currentTime
Later, in case you want to make a real time clock, you need to use setInterval to call updateTime every second.
setInterval(updateTime, 1000);
Like this.
And of course define <div id="counter"></div> in your html.
$(document).ready(function() {
function updateTime() {
var now = new Date();
var hours = now.getHours();
var minutes = now.getMinutes();
var seconds = now.getSeconds();
var currentTime = hours + ':' + minutes + ':' + seconds;
var counter = document.getElementById('counter');
counter.innerHTML = currentTime;
}
updateTime();
setInterval(updateTime, 1000);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="counter"></div>

newDate()// wrong
should be new Date();
counter.innerHTML = currenTime;
should be counter.innerHTML = currentTime;
use a setInterval
http://jsfiddle.net/rkv0deqc/
$(document).ready(function() {
var counter = document.getElementById('counter');
window.setInterval(function() {
console.log(1);
var now = new Date();
var hours = now.getHours();
var minutes = now.getMinutes();
var seconds = now.getSeconds();
var currentTime = hours + ':' + minutes +':' + seconds;
counter.innerHTML = currentTime;
}
,'1000');
});

You missed the white space between new and Date(). You really should take a look at devtools before this.
Your function is executed at DOM ready, and it's done. What you want is to update every second. You need a setInterval, or recusive setTimeout.

function countdown(id, timer){
timer--;
daysRemain = Math.floor(timer / 86400);
amount = timer%86400;
hrsRemain = Math.floor(amount / 3600);
amount = timer%3600;
minsRemain = Math.floor(amount/60);
amount = timer%60;
secsRemain =Math.floor(amount);
// Pad the string with leading 0 if less than 2 chars long
if (secsRemain.length < 2) {
secsRemain = '0' + secsRemain;
}
// String format the remaining time
clock = daysRemain + ":" + hrsRemain + ":" + minsRemain + ":" + secsRemain;
document.getElementById(id).innerHTML = clock;
if ( timer > 0 ) {
// Time still remains, call this function again in 1 sec
setTimeout("countdown('" + id + "'," + timer + ")", 1000);
} else {
// Time is out! Hide the countdown
document.getElementById(id).innerHTML = 'Time Expired';
}
}
this is another way using javascript to create the timer clock

Running a Javascript Clock at 4x Speed [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Javascript to run the Clock (date and time) 4 times speeder
I'm trying to make a clock that starts at a time value (hh:mm:ss) that I've supplied, and runs at 4x speed (for the server time of an online game that runs 4x actual time). I've modified a free clock that I found online to do this, but it only works for every other minute (try the code below to see exactly what I mean if that doesn't make sense).
var customClock = (function () {
var timeDiff;
var timeout;
function addZ(n) {
return (n < 10 ? '0' : '') + n;
}
function formatTime(d) {
t1 = d.getHours();
t2 = d.getMinutes();
t3 = d.getSeconds() * 4;
if (t3 > 59) {
t3 = t3 - 60;
t2 = t2 + 1;
}
if (t2 > 59) {
t2 = t2 - 60;
t1 = t1 + 1;
}
if (t1 > 23) {
t1 = 0;
}
return addZ(t1) + ':' + addZ(t2) + ':' + addZ(t3);
}
return function (s) {
var now = new Date();
var then;
var lag = 1015 - now.getMilliseconds();
if (s) {
s = s.split(':');
then = new Date(now);
then.setHours(+s[0], +s[1], +s[2], 0);
timeDiff = now - then;
}
now = new Date(now - timeDiff);
document.getElementById('clock').innerHTML = formatTime(now);
timeout = setTimeout(customClock, lag);
}
}());
window.onload = function () {
customClock('00:00:00');
};
Any idea why this is happening? I'm pretty new to Javascript and this is definitely a little hack-ey. Thanks

i take the orginal time and substract it from the current then multiply it by 4 and add it to the orginal time. I think that should take care or the sync problem.
(function(){
var startTime = new Date(1987,08,13).valueOf() //save the date 13. august 1987
, interval = setInterval(function() {
var diff = Date.now() - startTime
//multiply the diff by 4 and add to original time
var time = new Date(startTime + (diff*4))
console.log(time.toLocaleTimeString())
}, 1000)
}())
How to use with a custom date (use the Date object)
Date(year, month, day, hours, minutes, seconds, milliseconds)

var lag = 1015 - now.getMilliseconds(); is attempting to "run this again a smidge (15 ms) after the next clock tick". Make this value smaller (divide by 4?), and this code will run more frequently.
Next up, get it to show 4x the current clock duration. Similar problem: multiply now's details by 4 either inside or outside formatTime()

I would first create a Clock constructor as follows:
function Clock(id) {
var clock = this;
var timeout;
var time;
this.hours = 0;
this.minutes = 0;
this.seconds = 0;
this.stop = stop;
this.start = start;
var element = document.getElementById(id);
function stop() {
clearTimeout(timeout);
}
function start() {
timeout = setTimeout(tick, 0);
time = Date.now();
}
function tick() {
time += 1000;
timeout = setTimeout(tick, time - Date.now());
display();
update();
}
function display() {
var hours = clock.hours;
var minutes = clock.minutes;
var seconds = clock.seconds;
hours = hours < 10 ? "0" + hours : "" + hours;
minutes = minutes < 10 ? "0" + minutes : "" + minutes;
seconds = seconds < 10 ? "0" + seconds : "" + seconds;
element.innerHTML = hours + ":" + minutes + ":" + seconds;
}
function update() {
var seconds = clock.seconds += 4;
if (seconds === 60) {
clock.seconds = 0;
var minutes = ++clock.minutes;
if (minutes === 60) {
clock.minutes = 0;
var hours = ++clock.hours;
if (hours === 24) clock.hours = 0;
}
}
}
}
Then you can create a clock and start it like this:
var clock = new Clock("clock");
clock.start();
Here's a demo: http://jsfiddle.net/Nt5XN/

Compute elapsed time [duplicate]

This question already has answers here:
How to measure time taken by a function to execute
(30 answers)
Closed 9 years ago.
I am looking for some JavaScript simple samples to compute elapsed time. My scenario is, for a specific point of execution in JavaScript code, I want to record a start time. And at another specific point of execution in JavaScript code, I want to record an end time.
Then, I want to calculate the elapsed time in the form of: how many Days, Hours, Minutes and Seconds are elapsed between end time and start time, for example: 0 Days, 2 Hours, 3 Minutes and 10 Seconds are elapsed.
Any reference simple samples? :-)
Thanks in advance,
George

Try something like this (FIDDLE)
// record start time
var startTime = new Date();
...
// later record end time
var endTime = new Date();
// time difference in ms
var timeDiff = endTime - startTime;
// strip the ms
timeDiff /= 1000;
// get seconds (Original had 'round' which incorrectly counts 0:28, 0:29, 1:30 ... 1:59, 1:0)
var seconds = Math.round(timeDiff % 60);
// remove seconds from the date
timeDiff = Math.floor(timeDiff / 60);
// get minutes
var minutes = Math.round(timeDiff % 60);
// remove minutes from the date
timeDiff = Math.floor(timeDiff / 60);
// get hours
var hours = Math.round(timeDiff % 24);
// remove hours from the date
timeDiff = Math.floor(timeDiff / 24);
// the rest of timeDiff is number of days
var days = timeDiff ;

Try this...
function Test()
{
var s1 = new StopWatch();
s1.Start();
// Do something.
s1.Stop();
alert( s1.ElapsedMilliseconds );
}
// Create a stopwatch "class."
StopWatch = function()
{
this.StartMilliseconds = 0;
this.ElapsedMilliseconds = 0;
}
StopWatch.prototype.Start = function()
{
this.StartMilliseconds = new Date().getTime();
}
StopWatch.prototype.Stop = function()
{
this.ElapsedMilliseconds = new Date().getTime() - this.StartMilliseconds;
}

Hope this will help:
<!doctype html public "-//w3c//dtd html 3.2//en">
<html>
<head>
<title>compute elapsed time in JavaScript</title>
<script type="text/javascript">
function display_c (start) {
window.start = parseFloat(start);
var end = 0 // change this to stop the counter at a higher value
var refresh = 1000; // Refresh rate in milli seconds
if( window.start >= end ) {
mytime = setTimeout( 'display_ct()',refresh )
} else {
alert("Time Over ");
}
}
function display_ct () {
// Calculate the number of days left
var days = Math.floor(window.start / 86400);
// After deducting the days calculate the number of hours left
var hours = Math.floor((window.start - (days * 86400 ))/3600)
// After days and hours , how many minutes are left
var minutes = Math.floor((window.start - (days * 86400 ) - (hours *3600 ))/60)
// Finally how many seconds left after removing days, hours and minutes.
var secs = Math.floor((window.start - (days * 86400 ) - (hours *3600 ) - (minutes*60)))
var x = window.start + "(" + days + " Days " + hours + " Hours " + minutes + " Minutes and " + secs + " Secondes " + ")";
document.getElementById('ct').innerHTML = x;
window.start = window.start - 1;
tt = display_c(window.start);
}
function stop() {
clearTimeout(mytime);
}
</script>
</head>
<body>
<input type="button" value="Start Timer" onclick="display_c(86501);"/> | <input type="button" value="End Timer" onclick="stop();"/>
<span id='ct' style="background-color: #FFFF00"></span>
</body>
</html>

Something like a "Stopwatch" object comes to my mind:
Usage:
var st = new Stopwatch();
st.start(); //Start the stopwatch
// As a test, I use the setTimeout function to delay st.stop();
setTimeout(function (){
st.stop(); // Stop it 5 seconds later...
alert(st.getSeconds());
}, 5000);
Implementation:
function Stopwatch(){
var startTime, endTime, instance = this;
this.start = function (){
startTime = new Date();
};
this.stop = function (){
endTime = new Date();
}
this.clear = function (){
startTime = null;
endTime = null;
}
this.getSeconds = function(){
if (!endTime){
return 0;
}
return Math.round((endTime.getTime() - startTime.getTime()) / 1000);
}
this.getMinutes = function(){
return instance.getSeconds() / 60;
}
this.getHours = function(){
return instance.getSeconds() / 60 / 60;
}
this.getDays = function(){
return instance.getHours() / 24;
}
}

var StopWatch = function (performance) {
this.startTime = 0;
this.stopTime = 0;
this.running = false;
this.performance = performance === false ? false : !!window.performance;
};
StopWatch.prototype.currentTime = function () {
return this.performance ? window.performance.now() : new Date().getTime();
};
StopWatch.prototype.start = function () {
this.startTime = this.currentTime();
this.running = true;
};
StopWatch.prototype.stop = function () {
this.stopTime = this.currentTime();
this.running = false;
};
StopWatch.prototype.getElapsedMilliseconds = function () {
if (this.running) {
this.stopTime = this.currentTime();
}
return this.stopTime - this.startTime;
};
StopWatch.prototype.getElapsedSeconds = function () {
return this.getElapsedMilliseconds() / 1000;
};
StopWatch.prototype.printElapsed = function (name) {
var currentName = name || 'Elapsed:';
console.log(currentName, '[' + this.getElapsedMilliseconds() + 'ms]', '[' + this.getElapsedSeconds() + 's]');
};
Benchmark
var stopwatch = new StopWatch();
stopwatch.start();
for (var index = 0; index < 100; index++) {
stopwatch.printElapsed('Instance[' + index + ']');
}
stopwatch.stop();
stopwatch.printElapsed();
Output
Instance[0] [0ms] [0s]
Instance[1] [2.999999967869371ms] [0.002999999967869371s]
Instance[2] [2.999999967869371ms] [0.002999999967869371s]
/* ... */
Instance[99] [10.999999998603016ms] [0.010999999998603016s]
Elapsed: [10.999999998603016ms] [0.010999999998603016s]
performance.now() is optional - just pass false into StopWatch constructor function.

This is what I am using:
Milliseconds to a pretty format time string:
function ms2Time(ms) {
var secs = ms / 1000;
ms = Math.floor(ms % 1000);
var minutes = secs / 60;
secs = Math.floor(secs % 60);
var hours = minutes / 60;
minutes = Math.floor(minutes % 60);
hours = Math.floor(hours % 24);
return hours + ":" + minutes + ":" + secs + "." + ms;
}

First, you can always grab the current time by
var currentTime = new Date();
Then you could check out this "pretty date" example at http://www.zachleat.com/Lib/jquery/humane.js
If that doesn't work for you, just google "javascript pretty date" and you'll find dozens of example scripts.
Good luck.

<script type="text/javascript">
<!-- Gracefully hide from old browsers
// Javascript to compute elapsed time between "Start" and "Finish" button clicks
function timestamp_class(this_current_time, this_start_time, this_end_time, this_time_difference) {
this.this_current_time = this_current_time;
this.this_start_time = this_start_time;
this.this_end_time = this_end_time;
this.this_time_difference = this_time_difference;
this.GetCurrentTime = GetCurrentTime;
this.StartTiming = StartTiming;
this.EndTiming = EndTiming;
}
//Get current time from date timestamp
function GetCurrentTime() {
var my_current_timestamp;
my_current_timestamp = new Date(); //stamp current date & time
return my_current_timestamp.getTime();
}
//Stamp current time as start time and reset display textbox
function StartTiming() {
this.this_start_time = GetCurrentTime(); //stamp current time
document.TimeDisplayForm.TimeDisplayBox.value = 0; //init textbox display to zero
}
//Stamp current time as stop time, compute elapsed time difference and display in textbox
function EndTiming() {
this.this_end_time = GetCurrentTime(); //stamp current time
this.this_time_difference = (this.this_end_time - this.this_start_time) / 1000; //compute elapsed time
document.TimeDisplayForm.TimeDisplayBox.value = this.this_time_difference; //set elapsed time in display box
}
var time_object = new timestamp_class(0, 0, 0, 0); //create new time object and initialize it
//-->
</script>
<form>
<input type="button" value="Start" onClick="time_object.StartTiming()"; name="StartButton">
</form>
<form>
<input type="button" value="Finish" onClick="time_object.EndTiming()"; name="EndButton">
</form>
<form name="TimeDisplayForm">
Elapsed time:
<input type="text" name="TimeDisplayBox" size="6">
seconds
</form>

write java program that enter elapsed time in seconds for any cycling event & the output format should be like (hour : minute : seconds ) for EX : elapsed time in 4150 seconds= 1:09:10