Tamia image preload es6

preload.js

// Image preload

import { ensureArray } from './util';

export default function preload(images, callback) {
	let done = () => {
		counter--;
		if (counter === 0) {
			callback(errors.length ? errors : null);
		}
	};
	let error = function() {
		errors.push(this.src);  // eslint-disable-line no-invalid-this
		done();
	};

	images = ensureArray(images);
	let counter = images.length;
	let errors = [];
	images.forEach((src) => {
		let img = new Image();
		img.onload = done;
		img.onerror = error;
		img.src = src;
	});
}