diff --git a/String/FormatPhoneNumber.js b/String/FormatPhoneNumber.js
index c1bbde8320..0a6fe6fc5b 100644
--- a/String/FormatPhoneNumber.js
+++ b/String/FormatPhoneNumber.js
@@ -1,17 +1,16 @@
-// function that takes 10 digits and returns a string of the formatted phone number
-// e.g.: 1234567890 -> (123) 456-7890
-
-const formatPhoneNumber = (numbers) => {
-  const numbersString = numbers.toString()
-  if ((numbersString.length !== 10) || isNaN(numbersString)) {
+/**
+ * @description - function that takes 10 digits and returns a string of the formatted phone number e.g.: 1234567890 -> (123) 456-7890
+ * @param {string} phoneNumber
+ * @returns {string} - Format to (XXX) XXX-XXXX pattern
+ */
+const formatPhoneNumber = (phoneNumber) => {
+  if ((phoneNumber.length !== 10) || isNaN(phoneNumber)) {
     // return "Invalid phone number."
-    throw new TypeError('Invalid phone number.')
+    throw new TypeError('Invalid phone number!')
   }
-  const arr = '(XXX) XXX-XXXX'.split('')
-  Array.from(numbersString).forEach(n => {
-    arr[arr.indexOf('X')] = n
-  })
-  return arr.join('')
+
+  let index = 0
+  return '(XXX) XXX-XXXX'.replace(/X/g, () => phoneNumber[index++])
 }
 
-export { formatPhoneNumber }
+export default formatPhoneNumber
diff --git a/String/test/FormatPhoneNumber.test.js b/String/test/FormatPhoneNumber.test.js
index 0e9febcb79..42ae24a8a9 100644
--- a/String/test/FormatPhoneNumber.test.js
+++ b/String/test/FormatPhoneNumber.test.js
@@ -1,23 +1,15 @@
-import { formatPhoneNumber } from '../FormatPhoneNumber'
-
-describe('PhoneNumberFormatting', () => {
-  it('expects to return the formatted phone number', () => {
-    expect(formatPhoneNumber('1234567890')).toEqual('(123) 456-7890')
-  })
-
-  it('expects to return the formatted phone number', () => {
-    expect(formatPhoneNumber(1234567890)).toEqual('(123) 456-7890')
-  })
+import formatPhoneNumber from '../FormatPhoneNumber'
 
+describe('Testing the formatPhoneNumber functions', () => {
   it('expects to throw a type error', () => {
-    expect(() => { formatPhoneNumber('1234567') }).toThrow('Invalid phone number.')
+    expect(() => formatPhoneNumber('1234567')).toThrow('Invalid phone number!')
+    expect(() => formatPhoneNumber('123456text')).toThrow('Invalid phone number!')
+    expect(() => formatPhoneNumber(12345)).toThrow('Invalid phone number!')
   })
 
-  it('expects to throw a type error', () => {
-    expect(() => { formatPhoneNumber('123456text') }).toThrow('Invalid phone number.')
-  })
-
-  it('expects to throw a type error', () => {
-    expect(() => { formatPhoneNumber(12345) }).toThrow('Invalid phone number.')
+  it('expects to return the formatted phone number', () => {
+    expect(formatPhoneNumber('1234567890')).toEqual('(123) 456-7890')
+    expect(formatPhoneNumber('2124323322')).toEqual('(212) 432-3322')
+    expect(formatPhoneNumber('1721543455')).toEqual('(172) 154-3455')
   })
 })