react-intl sample code using messages for locale

reactIntlSample.js

import React, { useState } from "react";
import { IntlProvider, FormattedMessage } from "react-intl";

const messages = {
  en: {
    "app.hello": "Hello"
  },
  fr: {
    "app.hello": "Bonjour"
  }
};

function App() {
  const [locale, setLocale] = useState("en");
  return (
    <IntlProvider locale={locale} messages={messages[locale]}>
      <button onClick={() => setLocale("en")}>en</button>
      <button onClick={() => setLocale("fr")}>fr</button>
        <FormattedMessage id="app.hello" />
    </IntlProvider>
  );
}
export default App;