JavaScript memoized recursion

memoizer.js

var MyApp = {};

MyApp.memoizer = function (memo, formula) {
  var recur, result;

  recur = function (n) {
    result = memo[n];
    if (typeof result !== 'number') {
      result = formula(recur, n);
      memo[n] = result;
    }
    return result;
  };
  return recur;
};

MyApp.fib = MyApp.memoizer([0, 1], function (recur, n) {
  return recur(n - 1) + recur(n - 2);
});

MyApp.fact = MyApp.memoizer([1, 1], function (recur, n) {
  return n * recur(n - 1);
});

var i;
for (i = 0; i <= 20; i += 1) {
  document.write(i + ": " + MyApp.fib(i) + ", " + MyApp.fact(i) + "<br />");
}