JavaScript quickstart

Quickstarts explain how to set up and run an app that calls a Google Workspace API.

Google Workspace quickstarts use the API client libraries to handle some details of the authentication and authorization flow. We recommend that you use the client libraries for your own apps. This quickstart uses a simplified authentication approach that is appropriate for a testing environment. For a production environment, we recommend learning about authentication and authorization before choosing the access credentials that are appropriate for your app.

Create a JavaScript web application that makes requests to the Gmail API.

Objectives

Set up your environment.
Set up the sample.
Run the sample.

Prerequisites

Node.js & npm installed.
A Google Cloud project.

A Google account with Gmail enabled.

Set up your environment

To complete this quickstart, set up your environment.

Enable the API

Before using Google APIs, you need to turn them on in a Google Cloud project. You can turn on one or more APIs in a single Google Cloud project.

In the Google Cloud console, enable the Gmail API.

Enable the API

Configure the OAuth consent screen

If you're using a new Google Cloud project to complete this quickstart, configure the OAuth consent screen and add yourself as a test user. If you've already completed this step for your Cloud project, skip to the next section.

In the Google Cloud console, go to Menu > APIs & Services > OAuth consent screen.
Go to OAuth consent screen
For User type select Internal, then click Create.
Complete the app registration form, then click Save and Continue.
For now, you can skip adding scopes and click Save and Continue. In the future, when you create an app for use outside of your Google Workspace organization, you must change the User type to External, and then, add the authorization scopes that your app requires.
Review your app registration summary. To make changes, click Edit. If the app registration looks OK, click Back to Dashboard.

Authorize credentials for a web application

To authenticate end users and access user data in your app, you need to create one or more OAuth 2.0 Client IDs. A client ID is used to identify a single app to Google's OAuth servers. If your app runs on multiple platforms, you must create a separate client ID for each platform.

In the Google Cloud console, go to Menu > APIs & Services > Credentials.
Go to Credentials
Click Create Credentials > OAuth client ID.
Click Application type > Web application.
In the Name field, type a name for the credential. This name is only shown in the Google Cloud console.
Add authorized URIs related to your app:
- Client-side apps (JavaScript)–Under Authorized JavaScript origins, click Add URI. Then, enter a URI to use for browser requests. This identifies the domains from which your application can send API requests to the OAuth 2.0 server.
- Server-side apps (Java, Python, and more)–Under Authorized redirect URIs, click Add URI. Then, enter an endpoint URI to which the OAuth 2.0 server can send responses.
Click Create. The OAuth client created screen appears, showing your new Client ID and Client secret.
Note the Client ID. Client secrets aren't used for Web applications.
Click OK. The newly created credential appears under OAuth 2.0 Client IDs.

Make a note of these credentials because you need them later in this quickstart.

Create an API key

In the Google Cloud console, go to Menu > APIs & Services > Credentials.
Go to Credentials
Click Create credentials > API key.
Your new API key is displayed.
- Click Copy to copy your API key for use in your app's code. The API key can also be found in the "API keys" section of your project's credentials.
- Click Restrict key to update advanced settings and limit use of your API key. For more details, see Applying API key restrictions.

Set up the sample

In your working directory, create a file named index.html.

In the index.html file, paste the following sample code:

gmail/quickstart/index.html

View on GitHub

<!DOCTYPE html>
<html>
  <head>
    <title>Gmail API Quickstart</title>
    <meta charset="utf-8" />
  </head>
  <body>
    <p>Gmail API Quickstart</p>

    <!--Add buttons to initiate auth sequence and sign out-->
    <button id="authorize_button" onclick="handleAuthClick()">Authorize</button>
    <button id="signout_button" onclick="handleSignoutClick()">Sign Out</button>

    <pre id="content" style="white-space: pre-wrap;"></pre>

    <script type="text/javascript">
      /* exported gapiLoaded */
      /* exported gisLoaded */
      /* exported handleAuthClick */
      /* exported handleSignoutClick */

      // TODO(developer): Set to client ID and API key from the Developer Console
      const CLIENT_ID = '<YOUR_CLIENT_ID>';
      const API_KEY = '<YOUR_API_KEY>';

      // Discovery doc URL for APIs used by the quickstart
      const DISCOVERY_DOC = 'https://www.googleapis.com/discovery/v1/apis/gmail/v1/rest';

      // Authorization scopes required by the API; multiple scopes can be
      // included, separated by spaces.
      const SCOPES = 'https://www.googleapis.com/auth/gmail.readonly';

      let tokenClient;
      let gapiInited = false;
      let gisInited = false;

      document.getElementById('authorize_button').style.visibility = 'hidden';
      document.getElementById('signout_button').style.visibility = 'hidden';

      /**
       * Callback after api.js is loaded.
       */
      function gapiLoaded() {
        gapi.load('client', initializeGapiClient);
      }

      /**
       * Callback after the API client is loaded. Loads the
       * discovery doc to initialize the API.
       */
      async function initializeGapiClient() {
        await gapi.client.init({
          apiKey: API_KEY,
          discoveryDocs: [DISCOVERY_DOC],
        });
        gapiInited = true;
        maybeEnableButtons();
      }

      /**
       * Callback after Google Identity Services are loaded.
       */
      function gisLoaded() {
        tokenClient = google.accounts.oauth2.initTokenClient({
          client_id: CLIENT_ID,
          scope: SCOPES,
          callback: '', // defined later
        });
        gisInited = true;
        maybeEnableButtons();
      }

      /**
       * Enables user interaction after all libraries are loaded.
       */
      function maybeEnableButtons() {
        if (gapiInited && gisInited) {
          document.getElementById('authorize_button').style.visibility = 'visible';
        }
      }

      /**
       *  Sign in the user upon button click.
       */
      function handleAuthClick() {
        tokenClient.callback = async (resp) => {
          if (resp.error !== undefined) {
            throw (resp);
          }
          document.getElementById('signout_button').style.visibility = 'visible';
          document.getElementById('authorize_button').innerText = 'Refresh';
          await listLabels();
        };

        if (gapi.client.getToken() === null) {
          // Prompt the user to select a Google Account and ask for consent to share their data
          // when establishing a new session.
          tokenClient.requestAccessToken({prompt: 'consent'});
        } else {
          // Skip display of account chooser and consent dialog for an existing session.
          tokenClient.requestAccessToken({prompt: ''});
        }
      }

      /**
       *  Sign out the user upon button click.
       */
      function handleSignoutClick() {
        const token = gapi.client.getToken();
        if (token !== null) {
          google.accounts.oauth2.revoke(token.access_token);
          gapi.client.setToken('');
          document.getElementById('content').innerText = '';
          document.getElementById('authorize_button').innerText = 'Authorize';
          document.getElementById('signout_button').style.visibility = 'hidden';
        }
      }

      /**
       * Print all Labels in the authorized user's inbox. If no labels
       * are found an appropriate message is printed.
       */
      async function listLabels() {
        let response;
        try {
          response = await gapi.client.gmail.users.labels.list({
            'userId': 'me',
          });
        } catch (err) {
          document.getElementById('content').innerText = err.message;
          return;
        }
        const labels = response.result.labels;
        if (!labels || labels.length == 0) {
          document.getElementById('content').innerText = 'No labels found.';
          return;
        }
        // Flatten to string to display
        const output = labels.reduce(
            (str, label) => `${str}${label.name}\n`,
            'Labels:\n');
        document.getElementById('content').innerText = output;
      }
    </script>
    <script async defer src="https://apis.google.com/js/api.js" onload="gapiLoaded()"></script>
    <script async defer src="https://accounts.google.com/gsi/client" onload="gisLoaded()"></script>
  </body>
</html>

Replace the following:

YOUR_CLIENT_ID: the client ID that you created when you authorized credentials for a web application.
YOUR_API_KEY: the API key that you created as a Prerequisite.

Run the sample

In your working directory, install the http-server package:
```
npm install http-server
```
In your working directory, start a web server:
```
npx http-server -p 8000
```

In your browser, navigate to http://localhost:8000.
You see a prompt to authorize access:
1. If you're not already signed in to your Google Account, sign in when prompted. If you're signed in to multiple accounts, select one account to use for authorization.
2. Click Accept.

Your JavaScript application runs and calls the Gmail API.