groupByArtist.js

{
    'Pearl Jam': [
      {
        artist: 'Pearl Jam',
        album: 'Ten',
        year: '1991',
      },
      {
        artist: 'Pearl Jam',
        album: 'Yield',
        year: '1998',
      },
    ],
    'Soundgarden': [
      {
        artist: 'Soundgarden',
        album: 'Badmotorfinger',
        year: '1991',
      },
      {
        artist: 'Soundgarden',
        album: 'Superunknown',
        year: '1994',
      },
    ]
  }