IdentityProvider

// Iframe displaying a page from the https://idp.example origin
const user_info = await IdentityProvider.getUserInfo({
  configUrl: "https://idp.example/fedcm.json",
  clientId: "client1234",
});

// IdentityProvider.getUserInfo() returns an array of user information.
if (user_info.length > 0) {
  // Returning accounts should be first, so the first account received
  // is guaranteed to be a returning account
  const name = user_info[0].name;
  const given_name = user_info[0].given_name;
  const display_name = given_name ? given_name : name;
  const picture = user_info[0].picture;
  const email = user_info[0].email;

  // ...

  // Render a personalized sign-in button using the information returned above
}