Listening to chat events

After you established a connection to the Twitch chat server, you can listen to events:

const followAgeListener = chatClient.onMessage(async (channel: string, user: string, text: string, msg: ChatMessage) => {
	if (text === '!followage') {
		const broadcasterId = msg.channelId!;
		const { data: [follow] } = await apiClient.channels.getChannelFollowers(broadcasterId, msg.userInfo.userId);

		if (follow) {
			const currentTimestamp = Date.now();
			const followStartTimestamp = follow.followDate.getTime();
			chatClient.say(channel, `@${user} You have been following for ${secondsToDuration((currentTimestamp - followStartTimestamp) / 1000)}!`);
		} else {
			chatClient.say(channel, `@${user} You are not following!`);
		}
	}
});

// later, when you don't need this command anymore:
chatClient.removeListener(followAgeListener);

A list of all chat events can be found in the ChatClient class reference.