convert array values

notes.js

var chordArrays = [
  {
    'chord type': 'minor',
    inversion: 'root',
    chords: [
      {
        'scale degree': 'II',
        notes: [1, 3, 5]
      },
      {
        'scale degree': 'III',
        notes: [2, 4, 6]
      },
      {
        'scale degree': 'VI',
        notes: [5, 0, 2]
      }
    ]
  },
  {
    'chord type': 'minor',
    inversion: 'first',
    chords: [
      {
        'scale degree': 'II',
        notes: [3, 5, 1]
      },
      {
        'scale degree': 'III',
        notes: [4, 6, 2]
      },
      {
        'scale degree': 'VI',
        notes: [0, 2, 5]
      }
    ]
  }
];

var scale = ['c', 'd', 'e', 'f', 'g', 'a', 'b'];

chordArrays.forEach(o => {
  o.chords.forEach(n => {
    n.notes = n.notes.map(i => (i = scale[i]));
  });
});

console.log(chordArrays);