main.js

/**
 * Copyright 2018, Google, LLC.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

var gapi = gapi || {};

/* eslint-disable no-unused-vars */

// [START load_auth2_library]
function loadAuthClient () {
  gapi.load('auth2', initGoogleAuth);
}
// [END load_auth2_library]

// [START init_google_auth]
function initGoogleAuth (clientId = 'YOUR_CLIENT_ID') {
  gapi.auth2.init({
    client_id: clientId,
    scope: 'https://www.googleapis.com/auth/userinfo.email'
  }).then(() => {
    document.getElementById('sign-in-btn').disabled = false;
  }).catch(err => {
    console.log(err);
  });
}
// [END init_google_auth]

// [START user_signin]
function signIn () {
  gapi.auth2.getAuthInstance().signIn().then(() => {
    document.getElementById('sign-in-btn').hidden = true;
    document.getElementById('sign-out-btn').hidden = false;
    document.getElementById('send-request-btn').disabled = false;
  }).catch(err => {
    console.log(err);
  });
}
// [END user_signin]

// [START send_sample_request]
function sendSampleRequest (projectId = 'YOUR_PROJECT_ID') {
  var user = gapi.auth2.getAuthInstance().currentUser.get();
  var idToken = user.getAuthResponse().id_token;
  var endpoint = `https://${projectId}.appspot.com/_ah/api/echo/v1/email`;
  var xhr = new XMLHttpRequest();
  xhr.open('GET', endpoint + '?access_token=' + encodeURIComponent(idToken));
  xhr.onreadystatechange = function () {
    if (this.readyState === XMLHttpRequest.DONE && this.status === 200) {
      window.alert(xhr.responseText);
    }
  };
  xhr.send();
}
// [END send_sample_request]

// [START user_signout]
function signOut () {
  gapi.auth2.getAuthInstance().signOut().then(() => {
    document.getElementById('sign-in-btn').hidden = false;
    document.getElementById('sign-out-btn').hidden = true;
    document.getElementById('send-request-btn').disabled = true;
  }).catch(err => {
    console.log(err);
  });
}
// [END user_signout]

/* eslint-enable no-unused-vars */