Develop Reference

Turn Javascript localStorage countdown timer into an animated Progress Bar

I was searching for a sitewide javascript timer, which does not reset when a page is changed, and I have stumbled onto this one, along with its demo.
This could be a stupid question, but I was wondering if this "minutes : seconds" timer format could be turned into an animated progress bar type of countdown, meaning that as the time passes, the bar should get smaller.
Here is the code I am currently using:
<div id="time"></div>
<script>
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;
}
console.log(parseInt(seconds))
window.localStorage.setItem("seconds",seconds)
window.localStorage.setItem("minutes",minutes)
}, 1000);
}
window.onload = function () {
sec = parseInt(window.localStorage.getItem("seconds"))
min = parseInt(window.localStorage.getItem("minutes"))
if (parseInt(min*sec)) {
var fiveMinutes = (parseInt(min*60)+sec);
} else{
var fiveMinutes = 60 * 45;
}
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};
</script>
Any ideas?

How to make this countdown repeat after the time runs out?

I'm very new to Javascript and I found myself stuck with this issue. I want to make this countdown repeat after the time runs out, however I'm not really sure how to do it, and my attempts to make it work failed. Would appreciate help how to do it, Thanks.
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) {
// here's the problem. not sure how to make it repeat
}
}, 1000);
}
window.onload = function () {
var fiveMinutes = 60 * 5,
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};
Tried using clearInterval() and setTimeout() but instead of it working the countdown either went past 00:00 (00:0-1 and so on) or just didn't work at all.

You can reset timer:
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);
}

What you're describing is a forever countdown.
Note that eventhough you specify 1000 in the setInterval(). The timer isn't precise, so the callback may fire less than or greater than 1000ms. It is much safer to capture the startTime and then calculate the currentTime when the callback fires and measure the elapsedTime. This will give a true indication of elapsed time regardless of whether the timer is running slow or fast.
Because of the reset requirement. I actually infer that the timer is an infinite loop. We run it forever. There is no description as to when the timer is aborted, so, we just continue measuring currentTime and note elapse.
I use elapsedTime = (currentTime - startTime) / 1000 to calculate the elapsed time in seconds. Then, I elapsed % duration to make the counter stop at the duration and reset. Finally, I flip the math countdown = duration - 1 - (elapsedTime % duration) so instead of counting up, it counts down.
We then break down countdown into the minutes and seconds components.
Below is a fully working example that uses jQuery.
function startTimer(duration, display) {
let startTime = Date.now();
setInterval(function() {
let currentTime = Date.now();
let elapsedTime = Math.floor((currentTime - startTime) / 1000);
let countdown = duration - 1 - (elapsedTime % duration);
let minutes = Math.floor(countdown / 60).toString().padStart(2, "0");
let seconds = (countdown % 60).toString().padStart(2, "0");
display.text(minutes + ":" + seconds);
}, 1000 );
}
let fiveMinutes = 60 * 5;
let display = $("#time");
startTimer(fiveMinutes, display);
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<label id="time">mm:ss</label>

How do you escape out of an alert box and resume flow of action? - Javascript

So i am writing a simple javascript timer, and at 30 seconds it prompts the user with an alert box if they would like to reset the count down or let it continue.
I am able to reset the timer however I get stuck when the user clicks cancel on the alert box.
I tried letting the timer just resume at its current time but that doesn't help as the alert box just keeps reappearing
I am still very new to javascript so I would like to stay using vanilla js till I get a deeper understanding of the fundamentals!
Any guidance would be greatly appreciated!
Heres my code:
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<30){
var message = confirm("Would you like to extend timer?");
if (message == true) {
timer = 60 * 1;
}
else{
timer = timer;
}
}
if (--timer < 0) {
timer = duration;
}
}, 1000);
}
function resetTimer() {
timer = 60 * 1;
}
window.onload = function () {
var fiveMinutes = 60 * 1,
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};

just put if(timer==30) instead of if(timer<30) so that exactly at count of 30 units of time, you get asked once for confirmation at that instance (However be aware that until the confirmation is done, prompts will keep popping up every second). if you extend it, it will again wait till your timer goes down to 30 unit, else it will simply go down to 0 and break out.

function startTimer(duration, display) {
var timer = duration,
minutes,
seconds;
function timerFunc() {
timer -= 1;
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 == 30) {
var message = confirm("Would you like to extend timer?");
if (message == true) {
timer = 60;
} else return alert("Your timer has been stopped.")
}
setTimeout(timerFunc, 1000);
}
timerFunc();
}

Java Script Count Down Timer resets whenever page refreshes

I have PHP page, where I added a countdown for 30 min. and as it ticks when I refresh the page or perform a query of 'insert' and redirect back to that page, the timer gets reset.
I want the timer to be constant and continue count without any interruptions when the page gets refreshed.
My code goes as:
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 * 30,
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="timer">
<div>Section</div>
<div class="time">
<strong>Time left: <span id="time">30:00</span></strong>
</div>
</div>
Any Help Is Appreciated..

Use html5 local storage to update the timer value and when page load occurs read the timer value from local storage. I guess no other way.

Whenever your PHP page loads, the javascript is loaded with it. So
window.onload = function () {
var fiveMinutes = 60 * 30,
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};
is called and the timer starts at 5 minutes.
One solution would be to do an Ajax request in window.onload and get the remaining time.
Another solution would be to set the fiveMinutes variable (obviously it should be renamed more appropriately) via PHP, if the javascript code is inside your PHP file, like
<script>
...
var timeLeft = <?php echo $timeLeft ?>;
...
</script>
The first solution is the standard way to go and the second one is the easy way to go.

As others have pointed out, you could use local storage (if the your target clients support this feature see here)
<script>
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;
timer = --timer;
if (timer >= 0) {
localStorage.setItem('time', timer);
//timer = duration;
}
}, 1000);
}
window.onload = function () {
var countDown = 60 * 30;
var oldVal = localStorage.getItem('time');
if (oldVal && oldVal > 0) {
countDown = oldVal;
}
var display = document.querySelector('#time');
startTimer(countDown, display);
};
</script>
edit: of course one must not forget to check whether the stored value is below zero.

As already pointed out, you could store the current time with localStorage.
To do so you would save both minutes and seconds in each interval tick:
function startTimer(duration, display) {
var timer = duration, minutes, seconds;
setInterval(function () {
minutes = parseInt(timer / 60, 10)
seconds = parseInt(timer % 60, 10);
localStorage.setItem("minutes", minutes); // <--
localStorage.setItem("seconds", seconds); // <--
And in the load function you'd read from them and set the starting value appropriately. It's important to note that values are always stored as strings, and as such, it would be necessary to parse them back to numbers before passing them through:
window.onload = function () {
var timeLeft = 60 * 30,
display = document.querySelector('#time');
var minutes = localStorage.getItem("minutes"); //read minutes
var seconds = localStorage.getItem("seconds"); //read seconds
if (minutes && seconds){
timeLeft = Number(minutes) * 60 + Number(seconds); //set time with val from storage
}
startTimer(timeLeft, display);
};
I changed the name of your fiveMinutes to timeLeft to better reflect what it holds, and parsed both values to numbers with Number().
It's also important to mention that while this does keep the value after refreshes, it doesn't "count" the time while the page was closed. So keep that in mind.

Instead of refreshing the whole page try to use Ajax for communication and modify your html page using javascript.

Create a countdown timer and redirect to another page after countdown comes to zero

I want create a countdown timer for som sections of my asp.net sites with javascript.
The timer starts from various minutes or seconds. After countdown comes to zero, I want stop the timer tick and do somethings like redirect to another page.
I've found this code from google and it's ok, but never stop after countdown comes to zero. please help me to fix this bug.
<head>
<script>
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) {
//window.location = "http://www.example.com";
clearInterval(timer);
}
}, 1000);
}
window.onload = function () {
var fiveMinutes = 60 * 5,
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};
</script>
</head>
<body>
<div>Registration closes in <span id="time">05:00</span></div>
<form id="form1" runat="server">
</form>
</body>

You have to clear what setInterval return. Something like this.
<script>
function startTimer(duration, display) {
var timer = duration, minutes, seconds;
var end =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) {
//window.location = "http://www.example.com";
clearInterval(end);
}
}, 1000);
}
window.onload = function () {
var fiveMinutes = 5,
display = document.querySelector('#time');
startTimer(fiveMinutes, display);
};
</script>
</head>
<body>
<div>Registration closes in <span id="time">05:00</span></div>
<form id="form1" runat="server">
</form>

Gotrank's accepted answer is great - one small bug though:
var fiveMinutes = 5,
...should be...
var fiveMinutes = 300,
...for five minutes (it is currently 5 seconds). I would have commented, but I don't have enough reputation points yet.