npm install google-auth-library

const {GoogleAuth} = require('google-auth-library');

/**
* Instead of specifying the type of client you'd like to use (JWT, OAuth2, etc)
* this library will automatically choose the right client based on the environment.
*/
async function main() {
  const auth = new GoogleAuth({
    scopes: 'https://www.googleapis.com/auth/cloud-platform'
  });
  const client = await auth.getClient();
  const projectId = await auth.getProjectId();
  const url = `https://dns.googleapis.com/dns/v1/projects/${projectId}`;
  const res = await client.request({ url });
  console.log(res.data);
}

main().catch(console.error);

const {OAuth2Client} = require('google-auth-library');
const http = require('http');
const url = require('url');
const open = require('open');
const destroyer = require('server-destroy');

// Download your OAuth2 configuration from the Google
const keys = require('./oauth2.keys.json');

/**
* Start by acquiring a pre-authenticated oAuth2 client.
*/
async function main() {
  const oAuth2Client = await getAuthenticatedClient();
  // Make a simple request to the People API using our pre-authenticated client. The `request()` method
  // takes an GaxiosOptions object.  Visit https://github.com/JustinBeckwith/gaxios.
  const url = 'https://people.googleapis.com/v1/people/me?personFields=names';
  const res = await oAuth2Client.request({url});
  console.log(res.data);

  // After acquiring an access_token, you may want to check on the audience, expiration,
  // or original scopes requested.  You can do that with the `getTokenInfo` method.
  const tokenInfo = await oAuth2Client.getTokenInfo(
    oAuth2Client.credentials.access_token
  );
  console.log(tokenInfo);
}

/**
* Create a new OAuth2Client, and go through the OAuth2 content
* workflow.  Return the full client to the callback.
*/
function getAuthenticatedClient() {
  return new Promise((resolve, reject) => {
    // create an oAuth client to authorize the API call.  Secrets are kept in a `keys.json` file,
    // which should be downloaded from the Google Developers Console.
    const oAuth2Client = new OAuth2Client(
      keys.web.client_id,
      keys.web.client_secret,
      keys.web.redirect_uris[0]
    );

    // Generate the url that will be used for the consent dialog.
    const authorizeUrl = oAuth2Client.generateAuthUrl({
      access_type: 'offline',
      scope: 'https://www.googleapis.com/auth/userinfo.profile',
    });

    // Open an http server to accept the oauth callback. In this simple example, the
    // only request to our webserver is to /oauth2callback?code=<code>
    const server = http
      .createServer(async (req, res) => {
        try {
          if (req.url.indexOf('/oauth2callback') > -1) {
            // acquire the code from the querystring, and close the web server.
            const qs = new url.URL(req.url, 'http://localhost:3000')
              .searchParams;
            const code = qs.get('code');
            console.log(`Code is ${code}`);
            res.end('Authentication successful! Please return to the console.');
            server.destroy();

            // Now that we have the code, use that to acquire tokens.
            const r = await oAuth2Client.getToken(code);
            // Make sure to set the credentials on the OAuth2 client.
            oAuth2Client.setCredentials(r.tokens);
            console.info('Tokens acquired.');
            resolve(oAuth2Client);
          }
        } catch (e) {
          reject(e);
        }
      })
      .listen(3000, () => {
        // open the browser to the authorize url to start the workflow
        open(authorizeUrl, {wait: false}).then(cp => cp.unref());
      });
    destroyer(server);
  });
}

main().catch(console.error);

const client = await auth.getClient();

client.on('tokens', (tokens) => {
  if (tokens.refresh_token) {
    // store the refresh_token in my database!
    console.log(tokens.refresh_token);
  }
  console.log(tokens.access_token);
});

const url = `https://dns.googleapis.com/dns/v1/projects/${projectId}`;
const res = await client.request({ url });
// The `tokens` event would now be raised if this was the first request

const tokens = await oauth2Client.getToken(code);
// Now tokens contains an access_token and an optional refresh_token. Save them.
oauth2Client.setCredentials(tokens);

// Generate the url that will be used for the consent dialog.
const authorizeUrl = oAuth2Client.generateAuthUrl({
  // To get a refresh token, you MUST set access_type to `offline`.
  access_type: 'offline',
  // set the appropriate scopes
  scope: 'https://www.googleapis.com/auth/userinfo.profile',
  // A refresh token is only returned the first time the user
  // consents to providing access.  For illustration purposes,
  // setting the prompt to 'consent' will force this consent
  // every time, forcing a refresh_token to be returned.
  prompt: 'consent'
});

// after acquiring an oAuth2Client...
const tokenInfo = await oAuth2Client.getTokenInfo('my-access-token');

// take a look at the scopes originally provisioned for the access token
console.log(tokenInfo.scopes);

const oAuth2Client = new OAuth2Client({
  clientId: <your_client_id>,
  redirectUri: <your_redirect_uri>
});

const {JWT} = require('google-auth-library');
const keys = require('./jwt.keys.json');

async function main() {
  const client = new JWT({
    email: keys.client_email,
    key: keys.private_key,
    scopes: ['https://www.googleapis.com/auth/cloud-platform'],
  });
  const url = `https://dns.googleapis.com/dns/v1/projects/${keys.project_id}`;
  const res = await client.request({url});
  console.log(res.data);
}

main().catch(console.error);

$ export CREDS='{
  "type": "service_account",
  "project_id": "your-project-id",
  "private_key_id": "your-private-key-id",
  "private_key": "your-private-key",
  "client_email": "your-client-email",
  "client_id": "your-client-id",
  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
  "token_uri": "https://accounts.google.com/o/oauth2/token",
  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
  "client_x509_cert_url": "your-cert-url"
}'

const {auth} = require('google-auth-library');

// load the environment variable with our keys
const keysEnvVar = process.env['CREDS'];
if (!keysEnvVar) {
  throw new Error('The $CREDS environment variable was not found!');
}
const keys = JSON.parse(keysEnvVar);

async function main() {
  // load the JWT or UserRefreshClient from the keys
  const client = auth.fromJSON(keys);
  client.scopes = ['https://www.googleapis.com/auth/cloud-platform'];
  const url = `https://dns.googleapis.com/dns/v1/projects/${keys.project_id}`;
  const res = await client.request({url});
  console.log(res.data);
}

main().catch(console.error);

const {auth, Compute} = require('google-auth-library');

async function main() {
  const client = new Compute({
    // Specifying the service account email is optional.
    serviceAccountEmail: 'my-service-account@example.com'
  });
  const projectId = await auth.getProjectId();
  const url = `https://dns.googleapis.com/dns/v1/projects/${projectId}`;
  const res = await client.request({url});
  console.log(res.data);
}

main().catch(console.error);

// Make a request to a protected Cloud Run service.
const {GoogleAuth} = require('google-auth-library');

async function main() {
  const url = 'https://cloud-run-1234-uc.a.run.app';
  const auth = new GoogleAuth();
  const client = await auth.getIdTokenClient(url);
  const res = await client.request({url});
  console.log(res.data);
}

main().catch(console.error);

// Make a request to a protected Cloud Identity-Aware Proxy (IAP) resource
const {GoogleAuth} = require('google-auth-library');

async function main()
  const targetAudience = 'iap-client-id';
  const url = 'https://iap-url.com';
  const auth = new GoogleAuth();
  const client = await auth.getIdTokenClient(targetAudience);
  const res = await client.request({url});
  console.log(res.data);
}

main().catch(console.error);

const {OAuth2Client} = require('google-auth-library');
// Expected audience for App Engine.
const expectedAudience = `/projects/your-project-number/apps/your-project-id`;
// IAP issuer
const issuers = ['https://cloud.google.com/iap'];
// Verify the token. OAuth2Client throws an Error if verification fails
const oAuth2Client = new OAuth2Client();
const response = await oAuth2Client.getIapCerts();
const ticket = await oAuth2Client.verifySignedJwtWithCertsAsync(
  idToken,
  response.pubkeys,
  expectedAudience,
  issuers
);

// Print out the info contained in the IAP ID token
console.log(ticket)