var getAllTrackIDs = new Promise(function(resolve, reject) {
    var trackIDs = [];
    /* Code to get trackIDs from HTML elements and add to array */
    if(trackIDs != 0) {
        resolve(trackIDs);
    }
    else {
        reject(Error("No trackIDs found"));
    }
});

var generateTracks = new Promise(function(resolve, reject) {
    var tracks = [];
    /* Code to generate tracks from TrackIDs and add to array */
    if(tracks != 0) {
        resolve(tracks);
    }
    else {
        reject(Error("Unable to generate tracks");
    }
});

getAllTrackIDs.then(generateTracks, function(message) {
    console.error(response);
}).then(function(response) {
    console.log("Done.");
}, function(response) {
    console.error(response);
});