refactored to use 1 method and commented the code.

Signed-off-by: Matt Bruce <mbrucedogs@gmail.com>

EmployeeDirectory/Extensions/String.swift

@@ -12,11 +12,9 @@ extension String {
     /// Non-numeric characters are removed, and formatting is applied based on the length of the string.
     /// - Returns: A formatted phone number as a string.
     internal func formatUSNumber() -> String {
-        // format the number
-        return format(with: "XXX-XXX-XXXX", phone: self)
-    }
-    
-    internal func format(with mask: String, phone: String) -> String {
+        // mask for the phone numver
+        let mask = "XXX-XXX-XXXX"
+        
         let numbers = filter { $0.isNumber }
         var result = ""
         var index = numbers.startIndex // numbers iterator
@@ -35,6 +33,6 @@ extension String {
             }
         }
         return result
-    }
+    }    
 }