added factorial number implementation

Author: namitmalasi

Factorial.js

@@ -0,0 +1,35 @@
+// Factorial of a non-negative integer, is multiplication of all integers smaller than or equal to n.
+
+// For example factorial of 6 is 6*5*4*3*2*1 which is 720.
+
+// Approach 1(For loop)
+
+function factorialWithFoorLoop(num) {
+  let result = 1;
+  for (let i = num; i > 0; i--) {
+    result *= i;
+  }
+  return result;
+}
+console.log(factorialWithFoorLoop(10));
+
+// Approach 2(While loop)
+
+function factorialWithWhileLoop(num) {
+  let result = 1;
+  while (num > 0) {
+    result *= num;
+    num--;
+  }
+  return result;
+}
+
+console.log(factorialWithWhileLoop(5));
+
+// Approach 3(Recursive)
+
+function factorialWithRecursion(num) {
+  if (num == 0) return 1;
+  else return num * factorialWithRecursion(num - 1);
+}
+console.log(factorialWithRecursion(10));