PublicKeyCredential.getClientExtensionResults()

getClientExtensionResults()

var publicKey = {
  // Here are the extensions (as "inputs")
  extensions: {
    "loc": true, // This extension has been defined to include location information in attestation
    "uvi": true  // user verification index: how the user was verified
  },
  challenge: new Uint8Array(16) /* from the server */,
  rp: {
    name: "Example CORP",
    id  : "login.example.com"
  },
  user: {
    id: new Uint8Array(16) /* from the server */,
    name: "[email protected]",
    displayName: "John Doe"
  },
  pubKeyCredParams: [
    {
      type: "public-key",
      alg: -7
    }
  ]
};

navigator.credentials.create({ publicKey })
  .then(function (newCredentialInfo) {
    var myBuffer = newCredentialInfo.getClientExtensionResults();
    // myBuffer will contain the result of any of the processing of the "loc" and "uvi" extensions
  }).catch(function (err) {
     console.error(err);
  });