Caching remote images in Titanium (asynchronously)

cache.js

export default class Utils {

    static loadCachedImageFromURL(url, cb) {
        let filename;

        try {
            filename = url.substring(url.lastIndexOf('/') + 1);
        } catch (err) {
            cb(null);
        }

        const imageFile = Ti.Filesystem.getFile(Ti.Filesystem.applicationCacheDirectory, filename);

        // If already cached: load from cache
        if (imageFile.exists()) {
            cb(imageFile.nativePath);
            return;
        }

        const httpClient = Ti.Network.createHTTPClient({
            onload: event => {
                if (!httpClient.responseData) {
                    Ti.API.error(event.error);
                    cb(null);
                    return;
                }

                imageFile.write(httpClient.responseData);
                cb(imageFile.nativePath);
            },
            onerror: event => {
                Ti.API.error('Could not load image:' + event.error);
            }
        });

        httpClient.open('GET', url);
        httpClient.send();
    }
}