text-input-controlled-input.js

import React, { useState } from 'react';
import { Text, TextInput, View } from 'react-native';

const Application = () => {
  const [text, setText] = useState('');
  function onChangeText(text) {
    setText(text.replaceAll(/[0-9]/g,'X'))
  }
  return (
    <View>
      <TextInput
        onChangeText={onChangeText}
        value={text}
      />
      <Text>
        {text}
      </Text>
    </View>
  );
}

export default Application;