“JavaScript Complex literal 2” Código de respuesta

JavaScript Complex literal 2

var recordCollection = {
  2548: {
    albumTitle: 'Slippery When Wet',
    artist: 'Bon Jovi',
    tracks: ['Let It Rock', 'You Give Love a Bad Name']
  },
  2468: {
    albumTitle: '1999',
    artist: 'Prince',
    tracks: ['1999', 'Little Red Corvette']
  },
  1245: {
    artist: 'Robert Palmer',
    tracks: []
  },
  5439: {
    albumTitle: 'ABBA Gold'
  }
};

// Only change code below this line
function updateRecords(records, id, prop, value) {
  if (value === '') {
    delete records[id][prop];
  } else if (prop === 'tracks') {
    records[id][prop] = records[id][prop] || []; // this is called shortcircuit evaluation, see below for explanation
    records[id][prop].push(value);
  } else {
    records[id][prop] = value;
  }
  return records;
}