Multi-param memoization

cached.js

Function.prototype.cached = function() {
  var f = this,
      cache = {};
  
  function get(c, a, i) {
    var l = a.length, k = a[i];
    if (l == 0) {
      return f();
    } else if (i==l) {
      return (k in c) ? c[k] : (c[k] = f.apply(this, a));
    } else {
      if (!(k in c)) c[k] = {};
      return get(c[k], a, i+1);
    }
  }
  
  return function() {
    return get(cache, [].slice.call(arguments), 0);
  }
}