Format Phone Number (JS)

formatPhoneNumber.js

var COUNTRY_CODE = "+62";

function formatPhoneNumber(phone) {
  var formatted = "";
  if (phone.substring(0, 3) !== COUNTRY_CODE) {
    if (phone.substring(0, 2) === COUNTRY_CODE.substr(1)) {
      formatted = COUNTRY_CODE + phone.slice(2);
    } else if (phone.substring(0, 1) === "0") {
      formatted = COUNTRY_CODE + phone.slice(1);
    } else {
      formatted = phone;
    }
  } else {
    formatted = phone;
  }
  return formatted;
}