add CheckKishnamurthyNumber

Maths/CheckKishnamurthyNumber.js

@@ -0,0 +1,40 @@
+/*
+    Problem statement and Explanation : https://www.geeksforgeeks.org/check-if-a-number-is-a-krishnamurthy-number-or-not-2/
+
+    krishnamurthy number is a number the sum of the all fectorial of the all dights is equal to the number itself.
+    145 => 1! + 4! + 5! = 1  + 24 + 120 = 145
+*/
+
+// factorail utility method.
+const factorial = (n) => {
+  let fact = 1
+  while (n !== 0) {
+    fact = fact * n
+    n--
+  }
+  return fact
+}
+
+/**
+ * krishnamurthy number is a number the sum of the factorial of the all dights is equal to the number itself.
+ * @param {Number} number a number for checking is krishnamurthy number or not.
+ * @returns return correspond boolean vlaue, if the number is krishnamurthy number return `true` else return `false`.
+ * @example 145 => 1! + 4! + 5! = 1  + 24 + 120 = 145
+ */
+const CheckKishnamurthyNumber = (number) => {
+  // firstly, check that input is a number or not.
+  if (typeof number !== 'number') {
+    return new TypeError('Argument is not a number.')
+  }
+  // create a variable to store the sum of all digits factorial.
+  let sumOfAllDigitFactorial = 0
+  // convert the number to string for convenience.
+  String(number).split('').map(digit => {
+    // split one by one digit and calculate factorial and store to the variable.
+    return (sumOfAllDigitFactorial += factorial(Number(digit)))
+  })
+  // if the sumOftheFactorial is equal to the given number it means the number is a Krishnamurthy number.
+  return sumOfAllDigitFactorial === number
+}
+
+module.exports = CheckKishnamurthyNumber