Google Oauth for Nodejs

authorize.js

// Authorization code extracted from google quickstart guide
// https://developers.google.com/sheets/api/quickstart/nodejs

const fs = require('fs')
const readline = require('readline')
const { OAuth2Client } = require('google-auth-library')

// If modifying these scopes, delete your previously saved credentials
// at ~/.credentials/sheets.googleapis.com-nodejs-quickstart.json
const SCOPES = ['https://www.googleapis.com/auth/spreadsheets']
const TOKEN_DIR = '.credentials/'
const TOKEN_PATH = TOKEN_DIR + 'sheets.token.json'

module.exports = (cb) => {
// Load client secrets from a local file.
  fs.readFile('client_secret.json', (err, content) => {
    if (err) {
      console.log('Error loading client secret file: ' + err)
      return
    }
  // Authorize a client with the loaded credentials, then call the
  // Google Sheets API.
    authorize(JSON.parse(content), cb)
  })

/**
 * 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.
 */
  const authorize = (credentials, callback) => {
    const clientSecret = credentials.installed.client_secret
    const clientId = credentials.installed.client_id
    const redirectUrl = credentials.installed.redirect_uris[0]
    const oauth2Client = new OAuth2Client(clientId, clientSecret, redirectUrl)

  // Check if we have previously stored a token.
    fs.readFile(TOKEN_PATH, (err, token) => {
      if (err) {
        getNewToken(oauth2Client, callback)
      } else {
        oauth2Client.credentials = 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 to call with the authorized
 *     client.
 */
  const 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) {
          console.log('Error while trying to retrieve access token', err)
          return
        }
        oauth2Client.credentials = token
        storeToken(token)
        callback(oauth2Client)
      })
    })
  }

/**
 * Store token to disk be used in later program executions.
 *
 * @param {Object} token The token to store to disk.
 */
  function storeToken (token) {
    try {
      fs.mkdirSync(TOKEN_DIR)
    } catch (err) {
      if (err.code !== 'EEXIST') {
        throw err
      }
    }
    fs.writeFile(TOKEN_PATH, JSON.stringify(token))
    console.log('Token stored to ' + TOKEN_PATH)
  }
}