[bes]

bes,
Не взрывай мне мозг

лови fuel injection, possibly with slices of shit
ещё куча непокрытого, но твой случай покрывает

function type(el) {
	var type = typeof el;
	if ( type != "object" ) return type;
	if ( el == null ) return "null";
	if ( el.length || el.length >= 0 ) return "array";
	return "object";
}

function len(obj) {
	var n = 0;
	for (var key in obj) {
		n++;
	}
	return n;
}

function isEqual(obj1, obj2) {
	if ( type(obj1) != "object" && type(obj2) != "object" ) return obj1 == obj2;
	if ( len(obj1) != len(obj2) ) return false;
	for (var key in obj1) {
		if (obj1[key] === obj2[key]) {
			continue;
		}
		return false;
	}
	return true;
}

function cloneObject(obj) {
	var clone = {};
	for (var key in obj) {
		clone[key] = obj[key];
	}
	return clone;
}

function isSame(args1, args2) {
	var len1 = args1.length;
	var len2 = args2.length;
	if ( len1 != len2 ) return false;
	for (var i = 0; i < len1; i++) {
		if ( isEqual(args1[i], args2[i]) ) continue;
		return false;
	}
	return true;
}

function giblets(args) {
	var giblet = [];
	var length = args.length;
	for ( var i = 0; i < length; i++ ) {
		if ( type(args[i]) != "object" ) {
			giblet.push(args[i]);
		} else {
			giblet.push( cloneObject(args[i]) );
		}
	}
	return giblet;
}

function cacheFn(fn) {
	var cache = [];
	return function () {
		var len = cache.length;
		for (var i = 0; i < len; i++) {
			if ( isSame(cache[i].args, giblets(arguments)) ) {
				console.log("cache: " + cache[i].res + "\n\n");
				return cache[i].res;
			}
		}
		cache.push( {args: giblets(arguments), res: fn.apply(this, arguments)} );
		console.log("call: " + cache[len].res + "\n\n")
		return cache[len].res;
	}
}


function f(obj) {
	return obj.a + obj.b;
}

var cacheF = cacheFn(f);
o={b: 2}
var o1 = Object.create(o)
o1.a = 1
cacheF(o1);
cacheF(o1);
 
o.b=10
console.log("----");
cacheF(o1);
cacheF(o1);