Rocket.Chat/packages/rocketchat-slashcommands-kick/server.js

// Kick is a named function that will replace /kick commands

const Kick = function(command, params, {rid}) {
	if (command !== 'kick' || !Match.test(params, String)) {
		return;
	}
	const username = params.trim().replace('@', '');
	if (username === '') {
		return;
	}
	const user = Meteor.users.findOne(Meteor.userId());
	const kickedUser = RocketChat.models.Users.findOneByUsername(username);
	const room = RocketChat.models.Rooms.findOneById(rid);
	if (kickedUser == null) {
		return RocketChat.Notifications.notifyUser(Meteor.userId(), 'message', {
			_id: Random.id(),
			rid,
			ts: new Date,
			msg: TAPi18n.__('Username_doesnt_exist', {
				postProcess: 'sprintf',
				sprintf: [username]
			}, user.language)
		});
	}
	if ((room.usernames || []).includes(username) === false) {
		return RocketChat.Notifications.notifyUser(Meteor.userId(), 'message', {
			_id: Random.id(),
			rid,
			ts: new Date,
			msg: TAPi18n.__('Username_is_not_in_this_room', {
				postProcess: 'sprintf',
				sprintf: [username]
			}, user.language)
		});
	}
	Meteor.call('removeUserFromRoom', {rid, username});
};

RocketChat.slashCommands.add('kick', Kick);