Images loaded simple checker with promises

images-loaded.js

define(['promise'], function () {
    // Use any Promise polyfill
    
    var imgClasses = [HTMLImageElement],
        imgElementsList = ['img']

    if (window.HTMLPictureElement) {
        imgClasses.push(HTMLPictureElement)
        imgElementsList.push('picture')
    }

    imgElementsList = imgElementsList.join()

    function isAlreadyLoadedImage(img) {
        if (!img.complete) {
            return false
        }

        return !!img.naturalWidth
    }

    function isBrokenImage(img) {
        return img.complete && !img.naturalWidth
    }

    function onLoad(resolve) {
        resolve()
    }

    function onError(reject) {
        reject()
    }

    function offEvents(imgListenerLoad, imgListenerError) {
        this.removeEventListener('load', imgListenerLoad)
        this.removeEventListener('error', imgListenerError)
    }

    function isImage(element) {
        return imgClasses.some(function (imgClass) {
            return element instanceof imgClass
        })
    }

    return function imagesLoaded($element) {
        if (!$element) {
            return Promise.all([])
        }

        if (window.jQuery && $element instanceof window.jQuery || (window.Zepto && Zepto.zepto.Z === $element.constructor)) {
            $element = $element.get()
        }

        if ($element.length === undefined) {
            $element = [$element]
        }

        var promises = []

        Array.prototype.forEach.call($element, function (img) {
            if (!isImage(img)) {
                return promises.push(imagesLoaded(img.querySelectorAll(imgElementsList)))
            }

            var imgListenerLoad,
                imgListenerError

            var promise = new Promise(function (resolve, reject) {
                if (isAlreadyLoadedImage(img)) {
                    return resolve()
                }

                if (isBrokenImage(img)) {
                    return reject()
                }

                img.addEventListener('load', imgListenerLoad = onLoad.bind(img, resolve))
                img.addEventListener('error', imgListenerError = onError.bind(img, reject))
            })

            var undelegate = offEvents.bind(img, imgListenerLoad, imgListenerError)

            promise.then(undelegate, undelegate)

            promises.push(promise)
        })

        return Promise.all(promises)
    }
})