FormatPhoneNumber.js

/**
 * @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!')
 }

 let index = 0
 return '(XXX) XXX-XXXX'.replace(/X/g, () => phoneNumber[index++])
}

export default formatPhoneNumber