Non-blocking sleep semantics for JS

less-verbose.js

function loadImages (...images) {
	var imagesToLoad = images.length;

	var ready = return function;

	function imageReady () {
		if (!--imagesToLoad) {
			ready(null, images);
		}
	}

	function imageError (e) {
		ready(e);
	}

	images = images.map(function (src) {
		var img = new Image();
		img.src = src;
		img.onload = imageReady;
		img.onerror = imageError;
		return img;
	});
}

try {
	let [foo, bar, chuck] = loadImages('foo.gif', 'bar.png', 'chuck.jpg');
	console.log('All images loaded');
} catch (e) {
	console.error('There was an error loading an image:', e);
}

loadimages.js

function loadImages (...images) {
	var imagesToLoad = images.length;

	var ready = return function;

	function imageReady () {
		if (!--imagesToLoad) {
			ready(null, images);
		}
	}

	function imageError (e) {
		ready(e);
	}

	images = images.map(function (src) {
		var img = new Image();
		img.src = src;
		img.onload = imageReady;
		img.onerror = imageError;
		return img;
	});

	finally yield ready;
}

try {
	let [foo, bar, chuck] = yield loadImages('foo.gif', 'bar.png', 'chuck.jpg');
	console.log('All images loaded');
} catch (e) {
	console.error('There was an error loading an image:', e);
}