block13.js

// lib/validatePhone.js
...

const validatePhone = (phoneNumber) => {
  // validate there are no characters
  if (/[a-zA-Z]/.test(phoneNumber)) {
    return false;
  }
  // validate there are enough numbers
  const cleanNumber = phoneNumber.replace(/\s|\D/g, "");
  // validate country code
  if (cleanNumber[0] === "1") {
    return cleanNumber.length === 11;
  }
  return cleanNumber.length === 10;
};

export default validatePhone;