add GetGCD method

Maths/GetGCD.js

@@ -0,0 +1,26 @@
+/*
+    Problem statement and Explanation : https://en.wikipedia.org/wiki/Greatest_common_divisor
+
+    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) => {
+    // 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