Memoized Fibonacci Sequence

var fibo_useless = function(g, n) {
  return n == 0 ? 0 :
         n == 1 ? 1 :
         g(n-1) + g(n-2);
};

var cachify = function(f, cache) {
  return function(n) {
    if(!cache[n]) {
      var g = cachify(f, cache);
      cache[n] = f(g, n);
    }
    return cache[n];
  };
};

var cache = {};
var fibo_caching = cachify(fibo_useless, cache);

alert("fibo_caching(70) = " + fibo_caching(70)); // Very fast on the first call
alert("fibo_caching(70) = " + fibo_caching(70)); // Instantaneous on the second call