gapi auth2

google.service.ts

import { Injectable } from '@angular/core';

declare const gapi: any;

@Injectable()
export class GoogleService {

  constructor() { }

  authenticateUser(callback) {
    let auth2: any;

    gapi.load('auth2', function () {
      auth2 = gapi.auth2.init({
        client_id: 'apps.googleusercontent.com',
        cookiepolicy: 'single_host_origin',
        scope: 'profile email'
      });

      auth2.attachClickHandler(document.getElementById('google-login-button'), {},
      function (response) {

        const profile = response.getBasicProfile();
        const result = {
          uid: profile.getId(),
          name: profile.getName(),
          image: profile.getImageUrl(),
          provider: 'google',
          email: profile.getEmail(),
        };

        callback(result);
      });
    });
  };

  logout() {
    const home = window.location.href;
    const logout = 'https://www.google.com/accounts/Logout?continue=https://appengine.google.com/_ah/logout?continue=' + home;
    document.location.href = logout;
  }

}