Phone Input with formatter - see https://veb.co.nz/code/react/2019/07/25/react-native-phone-input.html

phoneInput.js

import React, { useState, useEffect } from 'react'
import { formatNumber } from "libphonenumber-js";
import { Image, View, TextInput } from 'react-native';

const App = ({ placeholder, onChange, confirm }) => {
  const [phoneNumber, setPhoneNumber] = useState('');

  useEffect(() => {
    let tempPhone = phoneNumber.replace(/\+/g, '');
    let removeSpaces = tempPhone.replace(/ /g, '');

    onChange(removeSpaces)
  }, [phoneNumber, onChange])

  const onBlur = () => {
    const formattedNumber = formatNumber(`+64${phoneNumber.replace(/^\+64/, "")}`, "International")
    setPhoneNumber(formattedNumber);
  };

  return (
    <View row>
      <Image
        source={require('app/images/flags/nz.png')}
        style=
      />
      <TextInput
        onBlur={onBlur}
        onChangeText={setPhoneNumber}
        placeholder={placeholder}
        hideUnderline
        value={phoneNumber}
        keyboardType={'phone-pad'} />
    </View>
  )


}

export default App;