diff --git a/lib/factorial.js b/lib/factorial.js
new file mode 100644
index 0000000..dd5da6b
--- /dev/null
+++ b/lib/factorial.js
@@ -0,0 +1,25 @@
+export function factorial(n) {
+  let result = 1;
+  for (let i = n; i > 1; i--) {
+    result *= i;
+  }
+  return result;
+}
+
+export function factorialRecursive(n) {
+  if (n < 2) {
+    return 1;
+  }
+
+  return n * factorialRecursive(n - 1);
+}
+
+// --------------------------- TESTS ---------------------------------------
+
+console.time("factorial time: ");
+factorial(1000);
+console.timeLog("factorial time: ");
+
+console.time("recursive factorial time: ");
+factorialRecursive(1000);
+console.timeLog("recursive factorial time: ");