An anonymous connection allows you to connect to Twitch without having to authenticate. This is ideal for chat overlays.

const tmi = require('tmi.js');

const client = new tmi.Client({
	channels: [ 'my_name' ]
});

client.connect();

client.on('message', (channel, tags, message, self) => {
	// "Alca: Hello, World!"
	console.log(`${tags['display-name']}: ${message}`);
});
					

Using authorization allows the bot to send messages on behalf of the authenticated account. Typically this would be a dedicated bot account, but it could be an interface for a user to send messages directly.

const tmi = require('tmi.js');

const client = new tmi.Client({
	options: { debug: true },
	identity: {
		username: 'my_bot_name',
		password: 'oauth:my_bot_token'
	},
	channels: [ 'my_name' ]
});

client.connect();

client.on('message', (channel, tags, message, self) => {
	// Ignore echoed messages.
	if(self) return;

	if(message.toLowerCase() === '!hello') {
		// "@alca, heya!"
		client.say(channel, `@${tags.username}, heya!`);
	}
});
					

This command handler example will split a message like this example chat message: !Echo Chat message here into the command "echo" with the arguments [ "Chat", "message", "here" ].

client.on('message', (channel, tags, message, self) => {
	if(self || !message.startsWith('!')) return;

	const args = message.slice(1).split(' ');
	const command = args.shift().toLowerCase();

	if(command === 'echo') {
		client.say(channel, `@${tags.username}, you said: "${args.join(' ')}"`);
	}
});