diff --git a/Javascript/Numbers/factorial.js b/Javascript/Numbers/factorial.js
new file mode 100644
index 0000000..d0e393c
--- /dev/null
+++ b/Javascript/Numbers/factorial.js
@@ -0,0 +1,10 @@
+// factorial method returns the factorial of a number
+const factorial = (n) => {
+  // firstly, check that input is a number or not.
+  if (typeof n !== 'number') {
+    return 'not a number.'
+  }
+  return n <= 1 ? 1 : n * factorial(n - 1)
+}
+
+console.log(factorial(5))