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
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> client<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

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();
  // List all buckets in a project.
  const url = `https://storage.googleapis.com/storage/v1/b?project=${projectId}`;
  const res = await client.request({ url });
  console.log(res.data);
}
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">function</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">:</span> <span class="token builtin">Promise</span><span class="token operator">&lt;</span><span class="token keyword">void</span><span class="token operator">></span></code></pre>

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);
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">class</span> <span class="token class-name">GoogleAuth</span>
<span class="token keyword">import</span> GoogleAuth</code></pre>

const { GoogleAuth, Impersonated } = require('google-auth-library');
const { SecretManagerServiceClient } = require('@google-cloud/secret-manager');

async function main() {

  // Acquire source credentials:
  const auth = new GoogleAuth();
  const client = await auth.getClient();

  // Impersonate new credentials:
  let targetClient = new Impersonated({
    sourceClient: client,
    targetPrincipal: 'impersonated-account@projectID.iam.gserviceaccount.com',
    lifetime: 30,
    delegates: [],
    targetScopes: ['https://www.googleapis.com/auth/cloud-platform']
  });

  // Get impersonated credentials:
  const authHeaders = await targetClient.getRequestHeaders();
  // Do something with `authHeaders.Authorization`.

  // Use impersonated credentials:
  const url = 'https://www.googleapis.com/storage/v1/b?project=anotherProjectID'
  const resp = await targetClient.request({ url });
  for (const bucket of resp.data.items) {
    console.log(bucket.name);
  }

  // Use impersonated credentials with google-cloud client library
  // Note: this works only with certain cloud client libraries utilizing gRPC 
  //    e.g., SecretManager, KMS, AIPlatform
  // will not currently work with libraries using REST, e.g., Storage, Compute
  const smClient = new SecretManagerServiceClient({
    projectId: anotherProjectID,
    auth: {
      getClient: () => targetClient,
    },
  });
  const secretName = 'projects/anotherProjectNumber/secrets/someProjectName/versions/1';
  const [accessResponse] = await smClient.accessSecretVersion({
    name: secretName,
  });

  const responsePayload = accessResponse.payload.data.toString('utf8');
  // Do something with the secret contained in `responsePayload`.
};

main();
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">class</span> <span class="token class-name">GoogleAuth</span>
<span class="token keyword">import</span> GoogleAuth</code></pre>

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();
  // List all buckets in a project.
  const url = `https://storage.googleapis.com/storage/v1/b?project=${projectId}`;
  const res = await client.request({ url });
  console.log(res.data);
}
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">function</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">:</span> <span class="token builtin">Promise</span><span class="token operator">&lt;</span><span class="token keyword">void</span><span class="token operator">></span></code></pre>

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);
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">class</span> <span class="token class-name">GoogleAuth</span>
<span class="token keyword">import</span> GoogleAuth</code></pre>

const auth = new GoogleAuth({
  scopes: 'https://www.googleapis.com/auth/cloud-platform',
  // Pass the project ID explicitly to avoid the need to grant `roles/browser` to the service account
  // or enable Cloud Resource Manager API on the project.
  projectId: 'CLOUD_RESOURCE_PROJECT_ID',
});
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> auth<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

// 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);
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">class</span> <span class="token class-name">GoogleAuth</span>
<span class="token keyword">import</span> GoogleAuth</code></pre>

// 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);
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">class</span> <span class="token class-name">GoogleAuth</span>
<span class="token keyword">import</span> GoogleAuth</code></pre>

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);
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">class</span> <span class="token class-name">GoogleAuth</span>
<span class="token keyword">import</span> GoogleAuth</code></pre>

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();
  // List all buckets in a project.
  const url = `https://storage.googleapis.com/storage/v1/b?project=${projectId}`;
  const res = await client.request({ url });
  console.log(res.data);
}
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">function</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">:</span> <span class="token builtin">Promise</span><span class="token operator">&lt;</span><span class="token keyword">void</span><span class="token operator">></span></code></pre>

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);
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">const</span> auth<span class="token operator">:</span> GoogleAuth
<span class="token keyword">import</span> auth</code></pre>

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);
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">const</span> auth<span class="token operator">:</span> GoogleAuth
<span class="token keyword">import</span> auth</code></pre>