// Permission strings in the same order as Discord calculates the bitset
let permissions = [
  'CREATE_INSTANT_INVITE',
  'KICK_MEMBERS',
  'BAN_MEMBERS',
  'ADMINISTRATOR',
  'MANAGE_CHANNELS',
  'MANAGE_GUILD',
  'ADD_REACTIONS',
  'VIEW_AUDIT_LOG',
  'PRIORITY_SPEAKER',
  'STREAM',
  'VIEW_CHANNEL',
  'SEND_MESSAGES',
  'SEND_TTS_MESSAGES',
  'MANAGE_MESSAGES',
  'EMBED_LINKS',
  'ATTACH_FILES',
  'READ_MESSAGE_HISTORY',
  'MENTION_EVERYONE',
  'USE_EXTERNAL_EMOJIS',
  'VIEW_GUILD_ANALYTICS',
  'CONNECT',
  'SPEAK',
  'MUTE_MEMBERS',
  'DEAFEN_MEMBERS',
  'MOVE_MEMBERS',
  'USE_VAD',
  'CHANGE_NICKNAME',
  'CHANGE_NICKNAMES',
  'MANAGE_ROLES',
  'MANAGE_WEBHOOKS',
  'MANAGE_EMOJIS'
];

// Old permission bitset
let old = (1 << 5) | (1 << 6);

// New permission bitset
let ne = (1 << 5); // <-- ADD_REACTIONS bit is missing

permissions.filter((_, i) => {
    return (old & (1 << i)) && !(ne & (1 << i));
}); // => ['ADD_REACTIONS']