nested_hash_map

            
/**
 * create map of shows, seasons, episodes
 * @param {data}
 * @returns {map}
 */
function ShowGuide(data){
    let showMap = new Map();
    let seasonMap;
    let season;
    let episodes;

    for (let i=0; i < data.length; i++){
        //if show exists retrieve it to insert more
        if (showMap.has(data[i].showid)){
            let show = showMap.get(data[i].showid);
            //if show and season already exist, insert episodes in map
            if (show.season.has(data[i].seasonnumber)){
                episodes = show.season.get(data[i].seasonnumber);
                episode = {
                    'episodenumber': data[i].episodenumber, 
                    'episodetitle': data[i].episodetitle
                };
                episodes.push(episode);
            } else {
                //season does not exist, insert season and episode in map
                episodes = [{
                    'episodenumber': data[i].episodenumber, 
                    'episodetitle': data[i].episodetitle
                }];
                show.season = seasonMap.set(data[i].seasonnumber, episodes);
            }
        } else {
            //show doesn't exist, create it with season and episode
            seasonMap = new Map();
            episodes = [{
                'episodenumber': data[i].episodenumber, 
                'episodetitle': data[i].episodetitle
            }];
            seasonMap.set(data[i].seasonnumber, episodes);
            showMap.set(data[i].showid, {'showtitle': data[i].showtitle, 'season': seasonMap});
        }
    }
    return showMap;
}

//data used in example
const data = [
    {"showid": 1234, "showtitle": "Game of Thrones", "seasonnumber": 1, "episodenumber": 1, "episodetitle": "Winter Is Coming"},
    {"showid": 1234, "showtitle": "Game of Thrones", "seasonnumber": 1, "episodenumber": 2, "episodetitle": "The Kingsroad"},
    {"showid": 1234, "showtitle": "Game of Thrones", "seasonnumber": 1, "episodenumber": 3, "episodetitle": "Lord Snow"},
    {"showid": 1234, "showtitle": "Game of Thrones", "seasonnumber": 2, "episodenumber": 1, "episodetitle": "The North Remembers"},
    {"showid": 1234, "showtitle": "Game of Thrones", "seasonnumber": 2, "episodenumber": 2, "episodetitle": "The Night Lands"},
    {"showid": 1234, "showtitle": "Game of Thrones", "seasonnumber": 2, "episodenumber": 3, "episodetitle": "What Is Dead May Never Die"},
    {"showid": 2345, "showtitle": "Stranger Things", "seasonnumber": 1, "episodenumber": 1, "episodetitle": "The Vanishing of Will Byers"},
    {"showid": 2345, "showtitle": "Stranger Things", "seasonnumber": 1, "episodenumber": 2, "episodetitle": "The Weirdo on Maple Street"},
    {"showid": 2345, "showtitle": "Stranger Things", "seasonnumber": 1, "episodenumber": 3, "episodetitle": "Holly, Jolly"},
    {"showid": 2345, "showtitle": "Stranger Things", "seasonnumber": 2, "episodenumber": 1, "episodetitle": "Madmax"},
    {"showid": 2345, "showtitle": "Stranger Things", "seasonnumber": 2, "episodenumber": 2, "episodetitle": "The Boy Who Came Back to Life" }
];

myShowGuide = new ShowGuide(data);
let gotShows = myShowGuide.get(1234);
let gotSeasonOne = gotShows.season.get(1);
let gotSeasonTwo = gotShows.season.get(2);
let stShows = myShowGuide.get(2345);
let stSeasonOne = stShows.season.get(1);
let stSeasonTwo = stShows.season.get(2);
let mapKeys = myShowGuide.keys();
let mapValues = myShowGuide.values();