Simple memoize wrapper

memoize.js

const argKey = x => x.toString() + ':' + typeof(x);
const generateKey = args => args.map(argKey).join('|');

const memoize = fn => {
	const cache = Object.create(null);
	return (...args) => {
		const key = generateKey(args);
		const val = cache[key];
		if (val) return val;
		const res = fn(...args);
		cache[key] = res;
		return res;
	};
};