Node.js quickstart

Complete the steps described in the rest of this page to create a simple Node.js command-line application that makes requests to the Gmail API.

Prerequisites

To run this quickstart, you need the following prerequisites:

  • Authorization credentials for a desktop application. To learn how to create credentials for a desktop application, refer to Create credentials.

  • A Google account with Gmail enabled.

Step 1: Install the client library

Run the following commands to install the libraries using npm:

npm install googleapis@39 --save

Step 2: Set up the sample

Create a file named index.js in your working directory and copy in the following code:

gmail/quickstart/index.js
const fs = require('fs');
const readline = require('readline');
const {google} = require('googleapis');

// If modifying these scopes, delete token.json.
const SCOPES = ['https://www.googleapis.com/auth/gmail.readonly'];
// The file token.json stores the user's access and refresh tokens, and is
// created automatically when the authorization flow completes for the first
// time.
const TOKEN_PATH = 'token.json';

// Load client secrets from a local file.
fs.readFile('credentials.json', (err, content) => {
  if (err) return console.log('Error loading client secret file:', err);
  // Authorize a client with credentials, then call the Gmail API.
  authorize(JSON.parse(content), listLabels);
});

/**
 * Create an OAuth2 client with the given credentials, and then execute the
 * given callback function.
 * @param {Object} credentials The authorization client credentials.
 * @param {function} callback The callback to call with the authorized client.
 */
function authorize(credentials, callback) {
  const {client_secret, client_id, redirect_uris} = credentials.installed;
  const oAuth2Client = new google.auth.OAuth2(
      client_id, client_secret, redirect_uris[0]);

  // Check if we have previously stored a token.
  fs.readFile(TOKEN_PATH, (err, token) => {
    if (err) return getNewToken(oAuth2Client, callback);
    oAuth2Client.setCredentials(JSON.parse(token));
    callback(oAuth2Client);
  });
}

/**
 * Get and store new token after prompting for user authorization, and then
 * execute the given callback with the authorized OAuth2 client.
 * @param {google.auth.OAuth2} oAuth2Client The OAuth2 client to get token for.
 * @param {getEventsCallback} callback The callback for the authorized client.
 */
function getNewToken(oAuth2Client, callback) {
  const authUrl = oAuth2Client.generateAuthUrl({
    access_type: 'offline',
    scope: SCOPES,
  });
  console.log('Authorize this app by visiting this url:', authUrl);
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  });
  rl.question('Enter the code from that page here: ', (code) => {
    rl.close();
    oAuth2Client.getToken(code, (err, token) => {
      if (err) return console.error('Error retrieving access token', err);
      oAuth2Client.setCredentials(token);
      // Store the token to disk for later program executions
      fs.writeFile(TOKEN_PATH, JSON.stringify(token), (err) => {
        if (err) return console.error(err);
        console.log('Token stored to', TOKEN_PATH);
      });
      callback(oAuth2Client);
    });
  });
}

/**
 * Lists the labels in the user's account.
 *
 * @param {google.auth.OAuth2} auth An authorized OAuth2 client.
 */
function listLabels(auth) {
  const gmail = google.gmail({version: 'v1', auth});
  gmail.users.labels.list({
    userId: 'me',
  }, (err, res) => {
    if (err) return console.log('The API returned an error: ' + err);
    const labels = res.data.labels;
    if (labels.length) {
      console.log('Labels:');
      labels.forEach((label) => {
        console.log(`- ${label.name}`);
      });
    } else {
      console.log('No labels found.');
    }
  });
}

Step 3: Run the sample

Run the sample using the following command:

node .

The first time you run the sample, it prompts you to authorize access:

  1. Browse to the provided URL in your web browser. If you are not already signed in to your Google account, you are prompted to sign in. If you are signed in to multiple Google accounts, you are asked to select one account to use for the authorization. If you don't have a browser on the machine running the code, and you've selected "Desktop app" when creating the OAuth client, you can browse to the URL provided on another machine, and then copy the authorization code back to the running sample.

  2. Click the Accept button.
  3. Copy the code you're given, paste it into the command-line prompt, and press Enter.

Notes

  • Authorization information is stored on the file system, so subsequent executions don't prompt for authorization.
  • The authorization flow in this example is designed for a command line application. For information on how to perform authorization in other contexts, see the Authorizing and Authenticating. section of the library's README.

Troubleshooting

This section describes some common issues that you may encounter while attempting to run this quickstart and suggests possible solutions.

This app isn't verified

If the OAuth consent screen displays the warning "This app isn't verified," your app is requesting scopes that provide access to sensitive user data. If your application uses sensitive scopes, your your app must go through the verification process to remove that warning and other limitations. During the development phase you can continue past this warning by clicking Advanced > Go to {Project Name} (unsafe).

Further reading

For further information on the APIs used in this quickstart, refer to the Google APIs Node.js Client section on GitHub.