Can't create a new object property using dot

I’m doing freecodecamp’s JS course and there’s a certain exercise I’m stuck with.

Here’s the code:

const 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'
  }
};

function updateRecords(records, id, prop, value) {
  if(prop !== 'tracks' && value !== ''){
    records.id[prop] = value;
  }
  return records;
}

updateRecords(recordCollection, 5439, 'artist', 'ABBA');

The line " records.id[prop] = value" gives me the error "TypeError: Cannot set properties of undefined ".
I don’t understand this since from what I know this should work. Any help?

Edit: by the way, records[id][prop] does work, which I’m not sure why. id is a given number which represents a property, why can’t I call it with dot notation?

You can only use bracket notation when you have a variable holding the property name. Dot notation can only be used when you have the exact, literal property name.