memoize.js

/* Function object extension to add memoization 
 * to any single-argument function.
*/

Function.prototype.memoized = function () {
	let key = JSON.stringify(arguments);
	this._cache = this._cache || {};
	this._cache[key] = this._cache[key] || 
		this.apply(this, arguments);

	return this._cache[key];
};

Function.prototype.memoize = function () {
	let fn = this;
	if (fn.lenth === 0 || fn.length > 1) {
		return fn;
	}

	return function () {
		return fn.memoized.apply(fn, arguments);
	};
};