Speed up your recursive functions with a memoizer.

Author: danielmiladinov

memoizer.js

@@ -0,0 +1,26 @@
+function memoizer(memo, formula) {
+    var recur = function (n) {
+        var result = memo[n];
+
+        if (typeof result !== 'number') {
+            result = formula(recur, n);
+            memo[n] = result;
+        }
+
+        return result;
+    };
+
+    return recur;
+};
+
+// The memo variable we pass is an array whose indexes are the inputs to the recursive function
+// and whose values are the outputs from the recursive function.
+// e.g. the factorial of 0 is 1, and the factorial of 1 is 1, hence the memo array: [1, 1]
+var factorial = memoizer([1, 1], function (recur, n) {
+    return n * recur(n - 1);
+});
+
+// The fibonacci of 0 is 0, and fibonacci of 1 is 1, hence the memo array: [0, 1]
+var fibonacci = memoizer([0, 1], function (recur, n) {
+    return recur(n - 1) + recur(n - 2);
+});