record-collection.js

// Setup var collection = { "2548": { "album": "Slippery When Wet", "artist": "Bon Jovi", "tracks": [ "Let It Rock", "You Give Love a Bad Name" ] }, "2468": { "album": "1999", "artist": "Prince", "tracks": [ "1999", "Little Red Corvette" ] }, "1245": { "artist": "Robert Palmer", "tracks": [ ] }, "5439": { "artist": "", "album": "ABBA Gold", "tracks": [ ] } }; // Keep a copy of the collection for tests var collectionCopy = JSON.parse(JSON.stringify(collection)); function updateRecords(id, prop, value) { if (prop == "artist" && value !== "") { collection[id].artist = value; } else if (prop == "tracks" && value !== "") { collection[id].tracks.push(value); } else if (prop == "tracks" && value === "") { delete collection[id].tracks; } else { delete collection[id].artist; } return collection; } // Alter values below to test your code updateRecords(2548, "tracks", "");