add type checking

Maths/GetEuclidGCD.js

@@ -0,0 +1,29 @@
+/*
+    Problem statement and Explanation : https://en.wikipedia.org/wiki/Euclidean_algorithm
+
+    In this method, we have followed the iterative approach to first
+    find a minimum of both numbers and go to the next step.
+*/
+
+/**
+ * GetGCD return the gcd of two numbers.
+ * @param {Number} arg1 first argument for gcd
+ * @param {Number} arg2 second argument for gcd
+ * @returns return a `gcd` value of both number.
+ */
+const getGcd = (arg1, arg2) => {
+  // firstly, check that input is a number or not.
+  if (typeof arg1 !== 'number' || typeof arg2 !== 'number') {
+    return new TypeError('Argument is not a number.')
+  }
+  // Find a minimum of both numbers.
+  let less = arg1 > arg2 ? arg2 : arg1
+  // Iterate the number and find the gcd of the number using the above explanation.
+  for (less; less >= 2; less--) {
+    if ((arg1 % less === 0) && (arg2 % less === 0)) return (less)
+  }
+
+  return (less)
+}
+
+module.exports = getGcd