class CollectionManager {
constructor(){
    this.collectionList = {};
}
initialize(collections){
    ...
}
populate(){
    var collectionObjs = Object.keys(this.collectionList).map(function(key){
        return collectionManager.collectionList[key];
    });
    return Promise.all(collectionObjs.map(function(collection){
        collection.populateVideos();
    }));
}
}

class Collection {
constructor(data){
    this.collectionInfo = data;
    this.videoArray = [];
}
populateVideos(){
    var collectionKey = this.collectionInfo.COLLECTIONID;
    var vChannels = Object.keys(this.collectionInfo.channels);
    return Promise.all(vChannels.map(requestVideos))
        .then(function (results) {
            var videoIdArray = [];
            return videoIdArray = [].concat.apply([], results);
        }).then(function(arrVideoIds){
            var groups = [];
            for (var i = 0; i < arrVideoIds.length; i += 50) {
                groups.push(arrVideoIds.slice(i, i + 50));
            }
            return groups;
        }).then(function(chunkedArrVideoIds){
            return Promise.all(chunkedArrVideoIds.map(requestVideoData)).then(function (results) {
                var videoTileArray = [].concat.apply([], results);
                collectionManager.collectionList[collectionKey].videoArray = videoTileArray;
                return videoTileArray;
            });
        });
}
displayCollection(){
    console.log(this.collectionInfo.COLLECTIONID);
    console.log(collectionManager.collectionList);
    console.log(collectionManager.collectionList[1]);
    console.log(collectionManager.collectionList[1].videoArray);

collectionManager.populate().then(
    function(){
        collectionManager.displayCollections()
    }
);