function to calculate factorial in JavaScript

seunzone · seunzone · commit e6087802edfa · 2017-10-29T14:57:14.000+01:00
diff --git a/factorial.js b/factorial.js
@@ -0,0 +1,68 @@
+// Challenge
+// Using the JavaScript language, have the function FirstFactorial(num) take the num parameter being passed and return the factorial of it (e.g. if num = 4, return (4 * 3 * 2 * 1)). For the test cases, the range will be between 1 and 18 and the input will always be an integer. 
+// Sample Test Cases
+// Input:4
+// Output:24
+
+// Input:8
+// Output:40320
+
+//========================================================//
+
+//========================================================//
+
+//========================================================//
+
+//1st method.
+function factorial(num) { 
+
+  var facto = 1;
+
+  for (var i = 1; i <= num; i++) {  
+    // multiply each number between 1 and num  
+    // factorial = 1 * 1 = 1
+    // factorial = 1 * 2 = 2
+    // factorial = 2 * 3 = 6
+    // factorial = 6 * 4 = 24
+    // ...
+    facto = facto * i;
+  }
+
+  return factorial;
+         
+}
+
+factorial(4); 
+factorial(10);
+factorial(9);
+factorial(5);
+//========================================================//
+
+//========================================================//
+
+//========================================================//
+
+// 2nd Method
+function factorial(num) { 
+
+  // our factorial function
+  function facto(n) { 
+ 
+    // terminate the recursion once we hit zero
+    if (n===0) { 
+    	return 1; 
+    }
+
+    // otherwise keep calling the function recursively 
+    else { 
+    	return facto(n-1) * n; 
+    }
+
+  }
+
+  return facto(num);
+         
+}
+   
+factorial(4);  
+
