never blocking loop mechanism, using setTimeout 0 trick and time control to break the loop and let the browser breath

optimizedFor.js

/**
* NEVER BLOCKING LOOP : implementation of the infamous setTimeout 0 hack, with time checking in order to guarantee fluidity without sacrificing execution speed.
*
* USAGE :
*	var array = ["a way too big array that is heavy to process"]
* optimizeFor({
*		nbIterations: array.length,
*		each:function( index ) {
*			doSomethingUsefulWith( array[ index ] );
*		},
*		end: function() {
*			console.log('ended processing array as fast as possible without blocking the browser');
*		}
*	);
*
* OPTIONS :
*	@nbIterations	: number of loops to execute (or a function that returns true / false)
*	@each : will be executed each time. iterationNumber will be given as an argument
*	@end 	: will be called once loop ends
*	@step	: max number of milliseconds a loop can block the browser. step up = loop runs faster, browser is less fluid. 0 = max fluidity, task last longer
*
*	DEPENDANCIES
*	namespace: window by default, but you dont want globals right ?
*	extend : jQuery OR underscorejs extend method
* noop : empty function, you can use $.noop
*/
(function (namespace, extend, noop) {
	namespace.optimizedFor = function(options) {
		// for IE10, or if you include a decent setImmediate polyfill (say https://github.com/YuzuJS/setImmediate)
		var setImmediate = window.setImmediate || function(callback) {
				setTimeout(callback, 0);
			},
			// native or polyfill way to have a number of milliseconds
			now = Date.now || function() {
					return Number(new Date);
				}
		;

		// replace ourselves
		namespace.optimizedFor = function optimizedFor(options) {

			options = extend({
				nbIterations: 0,
				each: noop,
				end: noop, //
				step: 40 //
			}, options);

			var i = 0,
				check;
			// allow the user to provide its own stop method
			if (typeof options.nbIterations === 'function') {
				check = options.nbIterations;
			} else {
				// by default, just check we can still
				check = function(i) {
					return i < options.nbIterations;
				};
			}

			(function mainLoop() {
				//
				for (var lastStart = now(); check(i); i++) {
					options.each(i);
					//
					if ((now() - lastStart) > 40) {
						// let the browser breath
						setImmediate(mainLoop);
						// break the loop but do not forget to increment
						i++;
						return;
					}
				}
				// final method (must be async too)
				setImmediate(options.end);
			}());
		};

		namespace.optimizedFor(options);
	};

}(window, $.extend, function(){}));