PublicKeyCredential: свойство rawId

const options = {
  challenge: new Uint8Array(26) /* from the server */,
  rp: {
    name: "Example CORP",
    id: "login.example.com",
  },
  user: {
    id: new Uint8Array(26) /* To be changed for each user */,
    name: "canand@example.com",
    displayName: "Carina Anand",
  },
  pubKeyCredParams: [
    {
      type: "public-key",
      alg: -7,
    },
  ],
};

navigator.credentials
  .create({ publicKey: options })
  .then((pubKeyCredential) => {
    const rawId = pubKeyCredential.rawId;
    // Do something with rawId
  })
  .catch((err) => {
    // Deal with any error
  });