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iOS6 webkit timer bug workaround

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ios6-timers.js
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(function (window) {
 
// This library re-implements setTimeout, setInterval, clearTimeout, clearInterval for iOS6.
// iOS6 suffers from a bug that kills timers that are created while a page is scrolling.
// This library fixes that problem by recreating timers after scrolling finishes (with interval correction).
// This code is released in the public domain. Do with it what you want, without limitations. I do not promise
// that it works, or that I will provide support (don't sue me).
// Author: rkorving@wizcorp.jp
 
var timeouts = {};
var intervals = {};
var orgSetTimeout = window.setTimeout;
var orgSetInterval = window.setInterval;
var orgClearTimeout = window.clearTimeout;
var orgClearInterval = window.clearInterval;
 
 
function createTimer(set, map, args) {
var id, cb = args[0], repeat = (set === orgSetInterval);
 
function callback() {
if (cb) {
cb.apply(window, arguments);
 
if (!repeat) {
delete map[id];
cb = null;
}
}
}
 
args[0] = callback;
 
id = set.apply(window, args);
 
map[id] = { args: args, created: Date.now(), cb: cb, id: id };
 
return id;
}
 
 
function resetTimer(set, clear, map, virtualId, correctInterval) {
var timer = map[virtualId];
 
if (!timer) {
return;
}
 
var repeat = (set === orgSetInterval);
 
// cleanup
 
clear(timer.id);
 
// reduce the interval (arg 1 in the args array)
 
if (!repeat) {
var interval = timer.args[1];
 
var reduction = Date.now() - timer.created;
if (reduction < 0) {
reduction = 0;
}
 
interval -= reduction;
if (interval < 0) {
interval = 0;
}
 
timer.args[1] = interval;
}
 
// recreate
 
function callback() {
if (timer.cb) {
timer.cb.apply(window, arguments);
if (!repeat) {
delete map[virtualId];
timer.cb = null;
}
}
}
 
timer.args[0] = callback;
timer.created = Date.now();
timer.id = set.apply(window, timer.args);
}
 
 
window.setTimeout = function () {
return createTimer(orgSetTimeout, timeouts, arguments);
};
 
 
window.setInterval = function () {
return createTimer(orgSetInterval, intervals, arguments);
};
 
window.clearTimeout = function (id) {
var timer = timeouts[id];
 
if (timer) {
delete timeouts[id];
orgClearTimeout(timer.id);
}
};
 
window.clearInterval = function (id) {
var timer = intervals[id];
 
if (timer) {
delete intervals[id];
orgClearInterval(timer.id);
}
};
 
window.addEventListener('scroll', function () {
// recreate the timers using adjusted intervals
// we cannot know how long the scroll-freeze lasted, so we cannot take that into account
 
var virtualId;
 
for (virtualId in timeouts) {
resetTimer(orgSetTimeout, orgClearTimeout, timeouts, virtualId);
}
 
for (virtualId in intervals) {
resetTimer(orgSetInterval, orgClearInterval, intervals, virtualId);
}
});
 
}(window));

This worked perfectly to fix a set of aggravating problems I was struggling with today. I would certainly not have figured out the problem by now if it wasn't for this gist and your comment on another web page linking here. Thank you so much for sharing this!

Does it solve this issue in other ios systems. I tried using it in a project but I still get on Ipad the interval only updating when the scrolling on a page stops. Am I missing something here?

Has anyone filed a radar against this issue?

You can use web worker to slove this problem, set a timer in your worker js, and postMessage to frontpage.

Thank you for this! I am continually getting an error just wondering if you might be able to diagnose it:

TypeError: 'undefined' is not a function (evaluating 'cb.apply(window, arguments)')

Looks like it's happening in the function that gets set during cb = args[0]

this causes libraries such as jquery.transit to not fire their callback.

thanks for the code.

Can anyone confirm is this problem has been resolved in iOS6.1?

I've tried it on iOS6.1, and it seems that the problem has gone away!

Hi.. I have added the fix.js in my header and issue seems to be fixed. But my images are inside a link (anchor tag), while clicking the image, its not redirecting. Just showing the loading icon and nothing happens after that. Please, need help on this :(

You don't need to track timers and intervals separately. You can pass interval IDs to clearTimeout, and the numbers will never overlap, since they use the same underlying list. http://www.whatwg.org/specs/web-apps/current-work/#dom-windowtimers-settimeout

novocaine: requestAnimationFrame isn't a great workaround, since it'll force a much longer delay for small timers (up to 16ms extra).

I wonder what the timing overhead of using a worker comes out to. The onscreen keyboard opening/closing inside a UIWebView (not in Safari) can also cause this issue.

@zewt I figured it wasn't required, but I also didn't want to introduce new cross-browser issues while trying to resolve one. Played it safe there. If all known browsers play nice with this, I guess that could be unified.

Although the bug is fixed in iOS 6.1, is anyone willing to document it on https://github.com/scottjehl/Device-Bugs for posterity? @pixelscript, can yours Radar issue description be used as Device Bugs issue description?

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