public/js/app.js
/**
  * @param {string} playlistId The unique id of the playlist object
  * @param {string} songId The unique id of the song object
  */
@param {string} playlistId The unique id of the playlist object
@param {string} songId The unique id of the song object
@param { string } playlistId The unique id of the playlist object @param { string } songId The unique id of the song object
function _addSong(playlistId, songId) {
  var index = _playlists.findIndex(function (p) {
    return p.id === playlistId;
  });
  _playlists[index].songIds.push(songId);
}
function _addSong ( playlistId , songId ) { var index = _playlists . findIndex ( function ( p ) { return p . id === playlistId ; } ) ; _playlists [ index ] . songIds . push ( songId ) ; }
@param {string} playlistId The unique id of the playlist object
 @param {string} songId The unique id of the song object
@param { string } playlistId The unique id of the playlist object @param { string } songId The unique id of the song object