when i use google.accounts.oauth2.initCodeClient, reported an error

const client = google.accounts.oauth2.initCodeClient({
  client_id: 'YOUR_GOOGLE_CLIENT_ID',
  scope: 'https://www.googleapis.com/auth/calendar.readonly',
  ux_mode: 'popup',
  callback: (response) => {
    const xhr = new XMLHttpRequest();
    xhr.open('POST', code_receiver_uri, true);
    xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    // Set custom header for CRSF
    xhr.setRequestHeader('X-Requested-With', 'XmlHttpRequest');
    xhr.onload = function() {
      console.log('Auth code response: ' + xhr.responseText);
    };
    xhr.send('code=' + code);
  },
});

1. When the popup mode is used in google.accounts.oauth2.initCodeClient(config: CodeClientConfig) and the redirect_uri is empty, when the server requests https://accounts.google.com/o/oauth2/token, what should the redirect_uri pass?
2. What is code_receiver_uri? what does？