ios6-timers.js

(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 free to use by anyone (MIT, blabla).
	// Original Author: rkorving@wizcorp.jp
	var timeouts = {};
	var intervals = {};
	var orgSetTimeout = window.setTimeout;
	var orgSetInterval = window.setInterval;
	var orgClearTimeout = window.clearTimeout;
	var orgClearInterval = window.clearInterval;
	// To prevent errors if loaded on older IE.
	if (!window.addEventListener) return false;
	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);
		}
	};
	//check and add listener on the top window if loaded on frameset/iframe
	var win = window;
	while (win.location != win.parent.location) {
		win = win.parent;
	}
	win.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));