// 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": {
      "album": "ABBA Gold"
    }
};
// Keep a copy of the collection for tests
var collectionCopy = JSON.parse(JSON.stringify(collection));

// Only change code below this line
function updateRecords(id, prop, value) {
  var album = collection[id]; // сначала находим альбом в collection по id

  if (value == '') { // If value is empty (""),
    delete album[prop]; // delete the given prop property from the album.
  } else if(prop != 'tracks') { // If prop isn't "tracks"
    if (value != '') { // and value isn't empty (""),
        album[prop] = value; // update or set the value for that record album's property.
    }
  }
  // выше мы проверили, что prop != 'tracks', значит этот блок else - для prop == 'tracks'
  else { // If prop is "tracks"
    if(!album.hasOwnProperty(prop)) { // but the album doesn't have a "tracks" property,
      album.tracks = []; //create an empty array before adding the new value to the album's corresponding property.
    }
    if (value != '') {
      album.tracks.push(value); // push the value onto the end of the album's existing tracks array.
    }
  return collection;
  }

  return collection;
}

// Alter values below to test your code
updateRecords(5439, "artist", "ABBA");