JS: Preload a set of images and fire a callback when all are loaded.

preloadImages.js

var preloadImages = function(imageSources, callback) {

	var images = [];

	var tryCallback = function() {
		var allImagesLoaded = (function(){
			for (var i = images.length; i--;) {
				if(!images[i].isLoaded){
					return false;
				}
			}
			return true;
		})();

		if(allImagesLoaded) {
			callback();
		}
	};

	for (var i = imageSources.length; i--;) {
		var imageSrc = imageSources[i];
		var image = document.createElement('img');
		images.push(image);
		image.onload = function() {
			this.isLoaded = true;
			tryCallback();
		};
		image.src = imageSrc;
	}
};

var callback = function() {
	console.log('OHHAI!')
};

preloadImages([
	'http://placekitten.com/1000/1000',
	'http://placekitten.com/300/1000',
	'http://placekitten.com/1000/2000'
], callback);

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