Vietnamese mobile phone number validation

phone-validation.js

const COUNTRY_DIALING_CODE = "84"

const NETWORKS_PREFIX = [
  // Viettel
  "32",
  "33",
  "34",
  "35",
  "36",
  "37",
  "38",
  "39",
  "86",
  "96",
  "97",
  "98",

  // MobiFone
  "70",
  "76",
  "77",
  "78",
  "79",
  "89",
  "90",
  "93",

  // Vinaphone
  "81",
  "82",
  "83",
  "84",
  "85",
  "88",
  "91",
  "94",

  // Vietnamobile
  "56",
  "58",
  "92",

  // Gmobile
  "59",
  "95",
  "99",
]

function isNotPhoneNumber(value) {
  return value.split("").some((character) => Number.isNaN(Number(character)))
}

export default function isPhoneNumberValid(value) {
  if (!value) {
    return false
  }

  // Remove whitespace and plus sign
  let formattedNumber = String(value).replace(/\s|\+/g, "")

  const isNotANumber = isNotPhoneNumber(formattedNumber)

  if (isNotANumber) {
    return false
  }

  // Length should be from 9 to 10 numbers
  // without COUNTRY_DIALING_CODE and zero number
  const startsWithCountryDialingCode = formattedNumber.startsWith(
    COUNTRY_DIALING_CODE,
  )

  if (startsWithCountryDialingCode) {
    formattedNumber = formattedNumber.substr(COUNTRY_DIALING_CODE.length)
  }

  const startsWithZero = formattedNumber.startsWith("0")

  if (startsWithZero) {
    formattedNumber = formattedNumber.substr(1)
  }

  // Have right prefix
  const networkPrefix = NETWORKS_PREFIX.find((prefix) =>
    formattedNumber.startsWith(prefix),
  )

  if (!networkPrefix) {
    return false
  }

  // Final length is always 7 numbers after remove NETWORKS_PREFIX
  // 84 166XXXXXXX
  // 84 96XXXXXXX
  formattedNumber = formattedNumber.substr(networkPrefix.length)

  if (formattedNumber.length !== 7) {
    return false
  }

  return true
}