My app is a game where a user has 30 mins to finish....node backend
Each time a user starts a game then a setInterval function is triggered server side....once 30mins is counted down then I clearInterval.
How do I make sure that each setInterval is unique to the particular user and the setInterval variable is not overwritten each time a new user starts a game? (or all setInterval's are cleared each time I clear).
Seems like I might need to create a unique "interval" variable for each new user that starts game??
Below code is triggered each time a new user starts a game
let secondsLeft = 300000;
let interval = setInterval(() => {
secondsLeft -= 1000;
if (secondsLeft === 0) {
console.log("now exit");
clearInterval(interval);
}
}, 10000);
Thanks!!
We used agenda for a pretty big strategy game backend which offers the benefit of persistence if the node app crashes etc.
We incorporated the user id into the job name and would then schedule the job, along with data to process, to run at a determined time specifying a handler to execute.
The handler would then run the job and perform the relevant tasks.
// create a unique jobname
const jobName = `${player.id}|${constants.events.game.createBuilding}`;
// define a job to run with handler
services.scheduler.define(jobName, checkCreateBuildingComplete);
// schedule it to run and pass the data
services.scheduler.schedule(at.toISOString(), jobName, {
id: id,
instance: instance,
started: when
});
Worked pretty well and offered decent protection against crashes. Maybe worth considering.
First: Concurrent Intervals and Timers are not the best design approach in JS, it is better to use one global timer and a list of objects storing the start, end, userid etc and update these in a loop.
Anyway. To have your interval id bound to a certain scope, you can use a Promise like so:
const createTimer = (duration, userid) => new Promise(res => {
const start = new Date().getTime();
let iid;
(function loop () {
const
now = new Date().getTime(),
delta = now - start
;
//elapsed
if (delta >= duration) {
clearTimeout(iid);
res(userid);
//try again later
} else {
iid = setTimeout(loop, 100)
}
})();
});
This way each timer will run »on its own«. I used setTimeout here since that wont requeue loop before it did everything it had to. It should work with setInterval as well and look like that:
const runTimer = (duration, userid, ontick) => new Promise(res => {
const
start = new Date().getTime(),
iid = setInterval(
() => {
const delta = new Date().getTime() - start;
if (delta < duration) {
//if you want to trigger something each time
ontick(delta, userid);
} else {
clearInterval(iid);
res(userid);
}
}, 500)
;
});
You do not even need a promise, a simple function will do as well, but then you have to build some solution for triggering stuff when the timer is elapsed.
Thanks #Chev and #philipp these are both good answers.
I was also made aware of a technique where you use an array for the setInterval variable.....this would make my code as follows;
let intervals = []
let secondsLeft = 300000;
intervals['i'+userId] = setInterval(() => {
secondsLeft -= 1000;
if (secondsLeft === 0) {
console.log("now exit");
clearInterval(interval);
}
}, 10000);
Does anyone else foresee this working?.
UPDATE 6.56pm PST.....it works!!
I'm new to javascript, and I've been stuck on this simple problem for days. I have a series of thousands of images (collectively a "dataset") that when viewed rapidly one after the other gives the appearance of video. I want to loop through all of my images.
I've created a function like so:
function updateImage(dataset, record_id) {
image_url = '/image?dataset='+dataset+'&record-id='+record_id;
if ($('#mpeg-image').length > 0) {
$('#mpeg-image')[0].src = image_url;
} else {
$("#image-thumbnail").html('<img id="mpeg-image", src="'+image_url+'"> </img>');
}
}
Calling the function once, e.g., updateImage('dataset_28_18-08-11',444); results in the image content updating in the browser. However, I want to show the images in a loop, so I created a function like this:
function playVideo() {
for (i = 0; i < 1800; i++) {
updateImage(dataset,i);
}
}
This function uses the same updateImage() function that worked above, but when I run playVideo(); Chrome doesn't update the image until the very end. The src tag changes, but the actual content does not. How can I alter my loop so that each image is loaded and shown in sequence? I don't want to use something like "Sprite" that merges all images into one, since that's too data intensive on my backend. I just want to load and show my images one after the other.
Browsers won't re-render page elements until there's a break in the execution of your code. Your entire image loop will run before the browser ever gets a chance to re-paint the images.
It's not because the loop "runs too fast" or because the images haven't loaded (though that can definitely pose problems). To see an example of redrawing issue, try changing your animation into an infinite loop, where it continually plays. The page will freeze ("pinwheel") forever and the page elements will never be updated, even long after all of your images have loaded. You need to give the browser an opportunity to redraw the page whenever you've made changes to page elements.
In web animation, this is often done via window.requestAnimationFrame() (see MDN docs). The method takes a callback function which is executed after the browser has redrawn the page. The browser will execute your callback once it's ready for page changes.
A simplistic example of this with you code would go something like this.
var imageNo = 0;
function step() {
updateImage(dataset, imageNo);
imageNo++;
if (imageNo < 1800) {
window.requestAnimationFrame(step);
}
}
window.requestAnimationFrame(step);
You can achieve a similar effect using setTimeout() or setInterval(), but those methods aren't optimized for animation.
The reason why you only see the last image is because of two things.
1. as #andriusain said, it takes the browser some indeterminate amount of time to download each image.
2. The loop runs so fast that the last iteration is what takes affect.
With that said, it would be best to either sprite the image (which it sounds like you can't do), or you can preload the images so that the browser caches them, then set the urls. You can do something like this.
// using es6
// I'd recommend adding <img src="mpeg-image" /> to your html page
// just to simplify the code. Also I recommend saving the image
// element in a local variable instead of using jQuery in each
// iteration loop which will definitely give a slower performance.
const mpegImgElement = $('#mpeg-image')[0];
const FPS = 30 / 1000; // 30 Frames Per Second
function playVideo() {
preLoadImages()
.then(urls => {
playUrls(urls);
})
.catch(error => {
console.log('error loading images', error);
})
}
function playUrls(urls) {
const index = 0;
const intervalId = setInterval(() => {
// set the url
mpegImgElement.src = urls[index];
// all done. stop the interval
if (++index === urls.length) {
clearInterval(intervalId);
}
}, FPS);
}
function preLoadImages() {
const promises = [];
for (i = 0; i < 1800; i++) {
const imageUrl = '/image?dataset='+dataset+'&record-id='+record_id;
const promise = loadImage(imageUrl);
promises.push(promise);
}
return Promise.all(promises);
}
function loadImage(url) {
return new Promise((resolve, reject) => {
const image = new Image();
image.addEventListener('load', () => {
resolve(url);
});
image.addEventListener('error', error => {
reject(error);
});
image.src = url;
});
}
This happens because the browser is still loading the images... I think your best bet is to programmatically load them first and once they are loaded then play the video... to do that maybe something like this will help:
var loadImages = function(images, callback) {
var loadTotal = 0;
for (var i = 0; i < images.length; i++) {
var image = new Image();
image.addEventListener('load', function() {
loadTotal++;
if (loadTotal === images.length) {
callback();
}
});
image.src = images[i];
}
}
var playVideo = function() {
// do stuff...
}
var images = ['image1.jpg', 'image2.jpg'];
loadImages(images, playVideo);
This idea is terrible.
JS is executed in single thread, while calling data from src is asynchronous method. Calling one by one and wait then definitely block the thread.
In this case you need promise to prepare all images first.
I make a workable example using google logo.
paths = ["https://www.google.com.hk/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png",
"https://www.google.com.hk/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png",
"https://www.google.com.hk/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png"]
var imgCount = paths.length;
function loadImage(url) {
return new Promise((resolve, reject) => {
let img = new Image();
img.addEventListener('load', e => resolve(img));
img.src = url;
});
}
promises = []
for (var i = 0; i < paths.length; i++){
path = paths[i];
promises.push(loadImage(path));
}
Promise.all(promises).then(imgs => {
imgs.forEach(e => document.getElementById('image-holder').appendChild(e));});
//What I done here is display then all, but you can make it like, replace one by one, or declare your own display function.
<div id="image-holder"></div>
I trying to create a rotating banner for cycle a few images.
const images = [url1, url2 url3]
const rotate = (url) => {
document.getElementById('banner').style.background = url
rotate(next)
}
Url's are correct full paths only shortened here in question. I'm striggl ing to solve how to get next in code above. This is some code I write from looking at examples. Im not a js programmer only recently started. Thank you for helping.
Here's one approach:
const rotate = (element, delay, urls) => {
let current = 0;
(function next() {
element.style.background = url[current]; // set image
current = (current + 1) % urls.length; // update for next pass
setTimeout(next, delay); // recycle
})(); // start immediately
};
with usage:
rotate(document.getElementById('banner'), 5000, [url1, url2, url3]);
The modulo arithmetic resets current to zero after the last image has been shown.
I'm using angularjs as front-end framework. I get a data set via a rest get call.
That contains coordinates in an array. What needs to be done is that array with coordinates should be iterated and should be shown in a map.
Once the user hits play in the map those coordinates should be displayed one ofter another having at least 1 second of interval.
And when user hits play button, the button it self converts to a pause button it should do what the name intend to do. pause the process. I couldn't achive this kind of behavior using angularjs. Following is the closest that I could come.
var getReplayData = function () {
return $http.get('http://localhost:4000/replay/asiri/vin/' + from + '/' + to);
};
$scope.play = function () {
from = rangeProperties.getFrom() * 1000;
to = rangeProperties.getTo() * 1000;
getReplayData().success(function (data) {
console.log(data);
var waitingTime = 0;
var gap = 0;
for (var i = 0; i < data.length; i++) {
(function (i) {
var element = data[i];
var coordinates = new Object();
coordinates.latitude = element.LATITUDE;
coordinates.longitude = element.LONGITUDE;
setTimeout(function () {
broadcastData(coordinates);
}, waitingTime);
if (i + 1 < data.length) {
gap = data[i + 1].TIMESTAMP - element.TIMESTAMP;
console.log(gap);
} else {
gap = 0;
}
waitingTime = waitingTime + gap;
})(i);
}
});
$scope.play refers to the play action of the button. I can't figure out how to pause this process. Seems like I might have to keep the references to all timeouts and cancel them. Any idea how to implement this kinda of scenario? I don't exactly need a code segment just an idea how to approach to solve this kinda of problem would be really nice.
Seems like I might have to keep the references to all timeouts and cancel them.
That would be a good first step.
I don't exactly need a code segment just an idea how to approach to solve this kinda of problem would be really nice
I would do the following:
cache the response data as a variable, if possible.
separate the play and pause functionality, tying them into a cancelable callback that you get from using the $interval service.
during playback, treat your coordinates data as a FIFO (queue), dequeuing the item which gets passed to the $interval's promise
during pause, you simply cancel the $interval promise
playing again doesn't require any fancy work on the queue as you'll resume the same logic on the first item in the queue when you resume.
I have a button which runs a long running function when it's clicked. Now, while the function is running, I want to change the button text, but I'm having problems in some browsers like Firefox, IE.
html:
<button id="mybutt" class="buttonEnabled" onclick="longrunningfunction();"><span id="myspan">do some work</span></button>
javascript:
function longrunningfunction() {
document.getElementById("myspan").innerHTML = "doing some work";
document.getElementById("mybutt").disabled = true;
document.getElementById("mybutt").className = "buttonDisabled";
//long running task here
document.getElementById("myspan").innerHTML = "done";
}
Now this has problems in firefox and IE, ( in chrome it works ok )
So I thought to put it into a settimeout:
function longrunningfunction() {
document.getElementById("myspan").innerHTML = "doing some work";
document.getElementById("mybutt").disabled = true;
document.getElementById("mybutt").className = "buttonDisabled";
setTimeout(function() {
//long running task here
document.getElementById("myspan").innerHTML = "done";
}, 0);
}
but this doesn't work either for firefox! the button gets disabled, changes colour ( due to the application of the new css ) but the text does not change.
I have to set the time to 50ms instead of just 0ms, in order to make it work ( change the button text ). Now I find this stupid at least. I can understand if it would work with just a 0ms delay, but what would happen in a slower computer? maybe firefox would need 100ms there in the settimeout? it sounds rather stupid. I tried many times, 1ms, 10ms, 20ms...no it won't refresh it. only with 50ms.
So I followed the advice in this topic:
Forcing a DOM refresh in Internet explorer after javascript dom manipulation
so I tried:
function longrunningfunction() {
document.getElementById("myspan").innerHTML = "doing some work";
var a = document.getElementById("mybutt").offsetTop; //force refresh
//long running task here
document.getElementById("myspan").innerHTML = "done";
}
but it doesn't work ( FIREFOX 21). Then i tried:
function longrunningfunction() {
document.getElementById("myspan").innerHTML = "doing some work";
document.getElementById("mybutt").disabled = true;
document.getElementById("mybutt").className = "buttonDisabled";
var a = document.getElementById("mybutt").offsetTop; //force refresh
var b = document.getElementById("myspan").offsetTop; //force refresh
var c = document.getElementById("mybutt").clientHeight; //force refresh
var d = document.getElementById("myspan").clientHeight; //force refresh
setTimeout(function() {
//long running task here
document.getElementById("myspan").innerHTML = "done";
}, 0);
}
I even tried clientHeight instead of offsetTop but nothing. the DOM does not get refreshed.
Can someone offer a reliable solution preferrably non-hacky ?
thanks in advance!
as suggested here i also tried
$('#parentOfElementToBeRedrawn').hide().show();
to no avail
Force DOM redraw/refresh on Chrome/Mac
TL;DR:
looking for a RELIABLE cross-browser method to have a forced DOM refresh WITHOUT the use of setTimeout (preferred solution due to different time intervals needed depending on the type of long running code, browser, computer speed and setTimeout requires anywhere from 50 to 100ms depending on situation)
jsfiddle: http://jsfiddle.net/WsmUh/5/
Webpages are updated based on a single thread controller, and half the browsers don't update the DOM or styling until your JS execution halts, giving computational control back to the browser. That means if you set some element.style.[...] = ... it won't kick in until your code finishes running (either completely, or because the browser sees you're doing something that lets it intercept processing for a few ms).
You have two problems: 1) your button has a <span> in it. Remove that, just set .innerHTML on the button itself. But this isn't the real problem of course. 2) you're running very long operations, and you should think very hard about why, and after answering the why, how:
If you're running a long computational job, cut it up into timeout callbacks (or, in 2019, await/async - see note at the end of this anser). Your examples don't show what your "long job" actually is (a spin loop doesn't count) but you have several options depending on the browsers you take, with one GIANT booknote: don't run long jobs in JavaScript, period. JavaScript is a single threaded environment by specification, so any operation you want to do should be able to complete in milliseconds. If it can't, you're literally doing something wrong.
If you need to calculate difficult things, offload it to the server with an AJAX operation (universal across browsers, often giving you a) faster processing for that operation and b) a good 30 seconds of time that you can asynchronously not-wait for the result to be returned) or use a webworker background thread (very much NOT universal).
If your calculation takes long but not absurdly so, refactor your code so that you perform parts, with timeout breathing space:
function doLongCalculation(callbackFunction) {
var partialResult = {};
// part of the work, filling partialResult
setTimeout(function(){ doSecondBit(partialResult, callbackFunction); }, 10);
}
function doSecondBit(partialResult, callbackFunction) {
// more 'part of the work', filling partialResult
setTimeout(function(){ finishUp(partialResult, callbackFunction); }, 10);
}
function finishUp(partialResult, callbackFunction) {
var result;
// do last bits, forming final result
callbackFunction(result);
}
A long calculation can almost always be refactored into several steps, either because you're performing several steps, or because you're running the same computation a million times, and can cut it up into batches. If you have (exaggerated) this:
var resuls = [];
for(var i=0; i<1000000; i++) {
// computation is performed here
if(...) results.push(...);
}
then you can trivially cut this up into a timeout-relaxed function with a callback
function runBatch(start, end, terminal, results, callback) {
var i;
for(var i=start; i<end; i++) {
// computation is performed here
if(...) results.push(...); }
if(i>=terminal) {
callback(results);
} else {
var inc = end-start;
setTimeout(function() {
runBatch(start+inc, end+inc, terminal, results, callback);
},10);
}
}
function dealWithResults(results) {
...
}
function doLongComputation() {
runBatch(0,1000,1000000,[],dealWithResults);
}
TL;DR: don't run long computations, but if you have to, make the server do the work for you and just use an asynchronous AJAX call. The server can do the work faster, and your page won't block.
The JS examples of how to deal with long computations in JS at the client are only here to explain how you might deal with this problem if you don't have the option to do AJAX calls, which 99.99% of the time will not be the case.
edit
also note that your bounty description is a classic case of The XY problem
2019 edit
In modern JS the await/async concept vastly improves upon timeout callbacks, so use those instead. Any await lets the browser know that it can safely run scheduled updates, so you write your code in a "structured as if it's synchronous" way, but you mark your functions as async, and then you await their output them whenever you call them:
async doLongCalculation() {
let firstbit = await doFirstBit();
let secondbit = await doSecondBit(firstbit);
let result = await finishUp(secondbit);
return result;
}
async doFirstBit() {
//...
}
async doSecondBit...
...
SOLVED IT!! No setTimeout()!!!
Tested in Chrome 27.0.1453, Firefox 21.0, Internet 9.0.8112
$("#btn").on("mousedown",function(){
$('#btn').html('working');}).on('mouseup', longFunc);
function longFunc(){
//Do your long running work here...
for (i = 1; i<1003332300; i++) {}
//And on finish....
$('#btn').html('done');
}
DEMO HERE!
As of 2019 one uses double requesAnimationFrame to skip a frame instead of creating a race condition using setTimeout.
function doRun() {
document.getElementById('app').innerHTML = 'Processing JS...';
requestAnimationFrame(() =>
requestAnimationFrame(function(){
//blocks render
confirm('Heavy load done')
document.getElementById('app').innerHTML = 'Processing JS... done';
}))
}
doRun()
<div id="app"></div>
As an usage example think of calculating pi using Monte Carlo in an endless loop:
using for loop to mock while(true) - as this breaks the page
function* piMonteCarlo(r = 5, yield_cycle = 10000){
let total = 0, hits = 0, x=0, y=0, rsqrd = Math.pow(r, 2);
while(true){
total++;
if(total === Number.MAX_SAFE_INTEGER){
break;
}
x = Math.random() * r * 2 - r;
y = Math.random() * r * 2 - r;
(Math.pow(x,2) + Math.pow(y,2) < rsqrd) && hits++;
if(total % yield_cycle === 0){
yield 4 * hits / total
}
}
}
let pi_gen = piMonteCarlo(5, 1000), pi = 3;
for(let i = 0; i < 1000; i++){
// mocks
// while(true){
// basically last value will be rendered only
pi = pi_gen.next().value
console.log(pi)
document.getElementById('app').innerHTML = "PI: " + pi
}
<div id="app"></div>
And now think about using requestAnimationFrame for updates in between ;)
function* piMonteCarlo(r = 5, yield_cycle = 10000){
let total = 0, hits = 0, x=0, y=0, rsqrd = Math.pow(r, 2);
while(true){
total++;
if(total === Number.MAX_SAFE_INTEGER){
break;
}
x = Math.random() * r * 2 - r;
y = Math.random() * r * 2 - r;
(Math.pow(x,2) + Math.pow(y,2) < rsqrd) && hits++;
if(total % yield_cycle === 0){
yield 4 * hits / total
}
}
}
let pi_gen = piMonteCarlo(5, 1000), pi = 3;
function rAFLoop(calculate){
return new Promise(resolve => {
requestAnimationFrame( () => {
requestAnimationFrame(() => {
typeof calculate === "function" && calculate()
resolve()
})
})
})
}
let stopped = false
async function piDOM(){
while(stopped==false){
await rAFLoop(() => {
pi = pi_gen.next().value
console.log(pi)
document.getElementById('app').innerHTML = "PI: " + pi
})
}
}
function stop(){
stopped = true;
}
function start(){
if(stopped){
stopped = false
piDOM()
}
}
piDOM()
<div id="app"></div>
<button onclick="stop()">Stop</button>
<button onclick="start()">start</button>
As described in the "Script taking too long and heavy jobs" section of Events and timing in-depth (an interesting reading, by the way):
[...] split the job into parts which get scheduled after each other. [...] Then there is a “free time” for the browser to respond between parts. It is can render and react on other events. Both the visitor and the browser are happy.
I am sure that there are many times in which a task cannot be splitted into smaller tasks, or fragments. But I am sure that there will be many other times in which this is possible too! :-)
Some refactoring is needed in the example provided. You could create a function to do a piece of the work you have to do. It could begin like this:
function doHeavyWork(start) {
var total = 1000000000;
var fragment = 1000000;
var end = start + fragment;
// Do heavy work
for (var i = start; i < end; i++) {
//
}
Once the work is finished, function should determine if next work piece must be done, or if execution has finished:
if (end == total) {
// If we reached the end, stop and change status
document.getElementById("btn").innerHTML = "done!";
} else {
// Otherwise, process next fragment
setTimeout(function() {
doHeavyWork(end);
}, 0);
}
}
Your main dowork() function would be like this:
function dowork() {
// Set "working" status
document.getElementById("btn").innerHTML = "working";
// Start heavy process
doHeavyWork(0);
}
Full working code at http://jsfiddle.net/WsmUh/19/ (seems to behave gently on Firefox).
If you don't want to use setTimeout then you are left with WebWorker - this will require HTML5 enabled browsers however.
This is one way you can use them -
Define your HTML and an inline script (you don't have to use inline script, you can just as well give an url to an existing separate JS file):
<input id="start" type="button" value="Start" />
<div id="status">Preparing worker...</div>
<script type="javascript/worker">
postMessage('Worker is ready...');
onmessage = function(e) {
if (e.data === 'start') {
//simulate heavy work..
var max = 500000000;
for (var i = 0; i < max; i++) {
if ((i % 100000) === 0) postMessage('Progress: ' + (i / max * 100).toFixed(0) + '%');
}
postMessage('Done!');
}
};
</script>
For the inline script we mark it with type javascript/worker.
In the regular Javascript file -
The function that converts the inline script to a Blob-url that can be passed to a WebWorker. Note that this might note work in IE and you will have to use a regular file:
function getInlineJS() {
var js = document.querySelector('[type="javascript/worker"]').textContent;
var blob = new Blob([js], {
"type": "text\/plain"
});
return URL.createObjectURL(blob);
}
Setup worker:
var ww = new Worker(getInlineJS());
Receive messages (or commands) from the WebWorker:
ww.onmessage = function (e) {
var msg = e.data;
document.getElementById('status').innerHTML = msg;
if (msg === 'Done!') {
alert('Next');
}
};
We kick off with a button-click in this demo:
document.getElementById('start').addEventListener('click', start, false);
function start() {
ww.postMessage('start');
}
Working example here:
http://jsfiddle.net/AbdiasSoftware/Ls4XJ/
As you can see the user-interface is updated (with progress in this example) even if we're using a busy-loop on the worker. This was tested with an Atom based (slow) computer.
If you don't want or can't use WebWorker you have to use setTimeout.
This is because this is the only way (beside from setInterval) that allow you to queue up an event. As you noticed you will need to give it a few milliseconds as this will give the UI engine "room to breeth" so-to-speak. As JS is single-threaded you cannot queue up events other ways (requestAnimationFrame will not work well in this context).
Hope this helps.
Update: I don't think in the long term that you can be sure of avoiding Firefox's aggressive avoidance of DOM updates without using a timeout. If you want to force a redraw / DOM update, there are tricks available, like adjusting the offset of elements, or doing hide() then show(), etc., but there is nothing very pretty available, and after a while when those tricks get abused and slow down user experience, then browsers get updated to ignore those tricks. See this article and the linked articles beside it for some examples: Force DOM redraw/refresh on Chrome/Mac
The other answers look like they have the basic elements needed, but I thought it would be worthwhile to mention that my practice is to wrap all interactive DOM-changing functions in a "dispatch" function which handles the necessary pauses needed to get around the fact that Firefox is extremely aggressive in avoiding DOM updates in order to score well on benchmarks (and to be responsive to users while browsing the internet).
I looked at your JSFiddle and customized a dispatch function the one that many of my programs rely on. I think it is self-explanatory, and you can just paste it into your existing JS Fiddle to see how it works:
$("#btn").on("click", function() { dispatch(this, dowork, 'working', 'done!'); });
function dispatch(me, work, working, done) {
/* work function, working message HTML string, done message HTML string */
/* only designed for a <button></button> element */
var pause = 50, old;
if (!me || me.tagName.toLowerCase() != 'button' || me.innerHTML == working) return;
old = me.innerHTML;
me.innerHTML = working;
setTimeout(function() {
work();
me.innerHTML = done;
setTimeout(function() { me.innerHTML = old; }, 1500);
}, pause);
}
function dowork() {
for (var i = 1; i<1000000000; i++) {
//
}
}
Note: the dispatching function also blocks calls from happening at the same time, because it can seriously confuse users if status updates from multiple clicks are happening together.
Fake an ajax request
function longrunningfunction() {
document.getElementById("myspan").innerHTML = "doing some work";
document.getElementById("mybutt").disabled = true;
document.getElementById("mybutt").className = "buttonDisabled";
$.ajax({
url: "/",
complete: function () {
//long running task here
document.getElementById("myspan").innerHTML = "done";
}
});}
Try this
function longRunningTask(){
// Do the task here
document.getElementById("mybutt").value = "done";
}
function longrunningfunction() {
document.getElementById("mybutt").value = "doing some work";
setTimeout(function() {
longRunningTask();
}, 1);
}
Some browsers don't handle onclick html attribute good. It's better to use that event on js object. Like this:
<button id="mybutt" class="buttonEnabled">
<span id="myspan">do some work</span>
</button>
<script type="text/javascript">
window.onload = function(){
butt = document.getElementById("mybutt");
span = document.getElementById("myspan");
butt.onclick = function () {
span.innerHTML = "doing some work";
butt.disabled = true;
butt.className = "buttonDisabled";
//long running task here
span.innerHTML = "done";
};
};
</script>
I made a fiddle with working example http://jsfiddle.net/BZWbH/2/
Have you tried adding listener to "onmousedown" to change the button text and click event for longrunning function.
Slightly modified your code at jsfiddle and:
$("#btn").on("click", dowork);
function dowork() {
document.getElementById("btn").innerHTML = "working";
setTimeout(function() {
for (var i = 1; i<1000000000; i++) {
//
}
document.getElementById("btn").innerHTML = "done!";
}, 100);
}
Timeout set to more reasonable value 100ms did the trick for me. Try it.
Try adjusting the latency to find the best value.
DOM buffer also exists in default browser on android,
long running javascript only flush DOM buffer once,
use setTimeout(..., 50) to solve it.
I have adapted Estradiaz's double animation frame method for async/await:
async function waitForDisplayUpdate() {
await waitForNextAnimationFrame();
await waitForNextAnimationFrame();
}
function waitForNextAnimationFrame() {
return new Promise((resolve) => {
window.requestAnimationFrame(() => resolve());
});
}
async function main() {
const startTime = performance.now();
for (let i = 1; i <= 5; i++) {
setStatus("Step " + i);
await waitForDisplayUpdate();
wasteCpuTime(1000);
}
const elapsedTime = Math.round(performance.now() - startTime);
setStatus(`Completed in ${elapsedTime} ms`);
}
function wasteCpuTime(ms) {
const startTime = performance.now();
while (performance.now() < startTime + ms) {
if (Math.random() == 0) {
console.log("A very rare event has happened.");
}
}
}
function setStatus(s) {
document.getElementById("status").textContent = s;
}
document.addEventListener("DOMContentLoaded", main);
Status: <span id="status">Start</span>