Get a distinct listing of all artists from a user's playlists using Apple Music API

get-distinct-playlist-artists.js

const axios = require('axios')

const userToken = '<user token>'
const devToken = '<dev token>'

/**
 * Gets a distinct array of the artists in a user's playlists
 * @param {string} devToken The Apple-issued JWT developer token
 * @param {string} userToken The returned Apple `musickit.authorize()` user token
 */
async function getArtists(devToken, userToken){
  const headers = {
    'Music-User-Token': userToken,
    'Authorization': `Bearer ${devToken}` 
  }

  /**
   * Destructure: playlists = data.data
   * @type {object[]}
   */
  const {data: {data: playlists}} = await axios.get('https://api.music.apple.com/v1/me/library/playlists', {
    headers
  })

  const playlistRequests = []

  playlists.forEach(playlist => {
    playlistRequests.push(axios.get(`https://api.music.apple.com/v1/me/library/playlists/${playlist.id}?include=tracks`, {
      headers
    }))
  })

  const playlistResponses = await Promise.all(playlistRequests)

  const artists = playlistResponses.reduce((builder, playlistResponse) => {
    /**
     * Destructure: tracks = data.data[0].relationships.tracks.data
     * @type {object[]}
     */
    const {data: {data: {0: {relationships: {tracks: {data: tracks}}}}}} = playlistResponse
    
    // Destructure: artistName = data.data[0].relationships.tracks.data[n].attributes.artistName
    tracks.forEach(({attributes: {artistName}}) => {
      if (!builder.includes(artistName)) {
        builder.push(artistName)
      }
    })

    return builder
  }, [])

  return artists
}

(async () => {
  const artists = await getArtists(devToken, userToken)
  console.log(artists)
})()