return image is loaded promise

imagePromise.js

/*!
 * return image is loaded promise
 * @param {String|Object} s image path string or HTML DOM Image Object
 * imagePromise(path_to_image).then(function (r) {
 * my_image_object.src = r;
 * }).catch (function (err) {
 * console.error("function manageImgLightboxLinks: image failed to load", err);
 * });
 * source: gist.github.com/englishextra/3e95d301d1d47fe6e26e3be198f0675e
 * passes jshint
 */
var imagePromise = function (s) {
	if (window.Promise) {
		return new Promise(function (y, n) {
			var f = function (e, p) {
				e.onload = function () {
					y(p);
				};
				e.onerror = function () {
					n(p);
				};
				e.src = p;
			};
			if ("string" === typeof s) {
				var a = new Image();
				f(a, s);
			} else {
				if ("IMG" !== s.tagName) {
					return Promise.reject();
				} else {
					if (s.src) {
						f(s, s.src);
					}
				}
			}
		});
	} else {
		throw new Error("Promise is not in window");
	}
};