我不是一个经验仍然在React.js，但我想写一些应用程序使用FingerprintJS。

function App() {
  let app_visitorId = 'Is not defined still';
  (async () => {
    // Get the visitor identifier when you need it.
    const fp = await fpPromise
    const result = await fp.get()
    // This is the visitor identifier:
    const visitorId = result.visitorId;
    const confidence = result.confidence;
    console.log(
        '----------------------------------------------------------\n' +
        'fingerprintjs@ visitorId: ' + visitorId + '\n' +
        'fingerprintjs@ confidence: ' + confidence.score.toPrecision(6) + '\n' +
        '----------------------------------------------------------\n');
  })();
  return (
      <div className="App">
        <header className="App-header">
          <img src={logo} className="App-logo" alt="logo" />
          <p>
            Edit <code>src/App.js</code> and save to reload.<br/>
            {app_visitorId}
          </p>
          <a
              className="App-link"
              href="https://reactjs.org"
              target="_blank"
              rel="noopener noreferrer"
          >
            Learn React
          </a>
        </header>
      </div>
  );
}

我的问题是：如何更改'app_visitorId' let以在render块中呈现其值？谢谢你！