https://www.tmijs.org/forums/index.php?/topic/78-need-some-help/

index.js

'use strict';

const tmi = require('tmi.js'),
	
	timerMessages = [],
	
	config = {
			identity: {
					username: '',
					password: ''
				},
			channel: 'punisher_biz'
		};

let client = new tmi.client({
			identity: config.identity,
			connection: {
					reconnect: true
				},
			channels: [config.channel]
		});

function isLive(channel) {
	if(arguments.length < 2) {
		throw new Error('Not enough arguments');
	}
	else if(typeof channel !== 'string') {
		throw new TypeError('channel is not a string');
	}
	return new Promise((resolve, reject) => {
		client.api({ // This is only how I would do it based on how you're doing it
				url: `https://api.twitch.tv/kraken/streams?channel=${channel}`,
				json: true, // Not necessary past tmi.js@1.0.0 for NodeJS tmi.js
			}, (err, response, body) => {
				if(err) {
					return reject(err);
				}
				resolve(body.hasOwnProperty('streams') && body.streams.length);
			});
	});
}

function createTimerMessage(time, cb) {
	function createInterval() {
		cleared = true;
		intervalID = setInterval(wrapped, time);
		return intervalID;
	}
	
	if(arguments.length < 1) {
		throw new Error('Not enough arguments');
	}
	else if(typeof time !== 'number') {
		throw new TypeError('time is not a number');
	}
	else if(typeof cb !== 'function') {
		throw new TypeError('cb is not a function');
	}
	else if(time < 10000) {
		throw new Error(`Interval time is probably too short! (${time/1000} second(s))`);
	}
	let args = [].slice.call(arguments, 2),
		wrapped = () => {
				if(client.readyState() === 'OPEN') {
					cb();
				}
			},
		intervalID = createInterval(),
		cleared = false,
		ret = {
				time: () => time,
				cb: () => cb,
				id: () => intervalID,
				state: () => !cleared,
				
				changeTime: _time => {
						time = _time;
						this.restart();
						return ret;
					},
				changeCB: _cb => {
						cb = _cb;
						this.restart();
						return ret;
					},
				restart: () => {
						this.stop();
						createInterval();
						return ret;
					},
				run: () => {
						if(this.state()) {
							this.restart();
						}
						wrapped();
						return ret;
					},
				stop: () => {
						clearInterval(intervalID);
						intervalID = undefined;
						cleared = true;
						return ret;
					},
			};
	return ret;
}

let followTimer = createTimerMessage(60*60*1000, () => { // Every hour
			isLive(config.channel)
			.then(live => {
					console.log('Status:', live);
					if(live) {
						client.say(config.channel, 'Bitte nicht vergessen mir zu folgen, Danke <3');
					}
				})
			.catch(e => console.log(e));
		});

timerMessages.push(followTimer);

client.connect();