Emitter.js

export class Emitter {
	constructor() {
		this.store = {};
	}

	on(eventList, handler) {
		if (typeof handler !== 'function') {
			throw new Error('Handler must be a function');
		}

		eventList.split(' ').forEach((event) => {
			if (!this.store[event]) this.store[event] = [];

			if (!this.store[event].includes(handler)) {
				this.store[event].push(handler);
			}
		});
	}

	once(eventList, handler) {
		const wrapper = (...args) => {
			handler.apply(this, args);
			this.off(eventList, wrapper);
		};

		this.on(eventList, wrapper);
	}

	off(name, handler) {
		if (this.store[name]) {
			this.store[name] = this.store[name].filter((h) => h !== handler);
		}
	}

	offAll(eventList) {
		eventList.split(' ').forEach((event) => {
			if (!this.store[event]) return;

			delete this.store[event];
		});
	}

	emit(name, payload) {
		if (!this.store[name]) return;

		this.store[name].forEach(async (handler) => {
			await handler.apply(this, [{...payload}]);
		});
	}

	clear() {
		this.store = {};
	}
}