store.js

class Store {
	constructor(reducer, initialState) {
		this.reducer = reducer;
		this.state = this.reducer(initialState, {});
		console.log('set state', this.state);
		this.listeners = [];
	}

	getState() {
		return this.state;
	}

	subscribe(listener) {
		this.listeners.push(listener);
	}

	dispatch(action) {
		this.state = this.reducer(this.state, action);
		this.listeners.forEach(listener => listener());
	}

	unsubscribe(listener) {
		this.listeners = this.listeners.filter((currListener) => {
			return currListener !== listener;
		});
	}
}