function getInitialPhoneDigits({
	value,
	phoneNumber,
	defaultCountry,
	international,
	useNationalFormat,
	metadata
}) {
	// If the `value` (E.164 phone number)
	// belongs to the currently selected country
	// and `useNationalFormat` is `true`
	// then convert `value` (E.164 phone number)
	// to a local phone number digits.
	// E.g. '+78005553535' -> '88005553535'.
	if ((international === false || useNationalFormat) && phoneNumber && phoneNumber.country) {
		return generateNationalNumberDigits(phoneNumber)
	}
	// If `international` property is `true`,
	// meaning "enforce international phone number format",
	// then always show country calling code in the input field.
	if (!value && international && defaultCountry) {
		return getInternationalPhoneNumberPrefix(defaultCountry, metadata)
	}
	return value
}
Gets initial "phone digits" (including `+`, if using international format).
@return {string} [phoneDigits] Returns `undefined` if there should be no initial "phone digits".