updateRecords.js

function updateRecords (id, prop, value) {
  if (prop === 'artist') {
    collection[id][prop] = value

    if (value === '') {
      delete collection[id][prop]
    }
  }

  else if (prop === 'tracks') {
    if (!collection[id]['tracks']) {
      collection[id][prop] = new Array(value)
    }

    else if (collection[id]['tracks'].length === 0) {
      collection[id]['tracks'].push(value)
    }

    else if (value === '') {
      delete collection[id]['tracks']
    }
  }

  return collection;
}