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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"
    }
};

function updateRecords(id, prop, value) {
  
  var isTracks = collection[id].hasOwnProperty("tracks"),
      newArray = [];
  
  if (prop === "album" || prop === "artist") {
    collection[id][prop] = value;
  } else if (prop === "tracks" && isTracks) {
      collection[id][prop].push(value);
  } else if (isTracks !== false) {
       collection[id][prop] = newArray;
       collection[id][prop].push(value);
  }  
  return collection;
}

updateRecords(5439, "tracks", "ABBA");