JAVASCRIPT

set a discord js v12 bot activity

// Set the client user's activity
client.user.setActivity('some activity ', { type: 'WATCHING' })
  .then(presence => console.log(`Activity set to ${presence.activities[0].name}`))
  .catch(console.error);

discord.js bot activity

bot.user.setActivity('some activity', { type: 'WATCHING' }) // STREAMING, WATCHING, CUSTOM_STATUS, PLAYING, COMPETING
.then(presence => console.log(`Activity set to ${presence.activities[0].name}`))
  .catch(console.error);