Get list of books from Google Books API

local.js

const apiKey = << API KEY HERE >>
const google = require('googleapis');
const serviceAccount = require('./key.json');
const { client_email, private_key } = serviceAccount;
const scope = 'https://www.googleapis.com/auth/books'

const client = new google.auth.JWT(client_email, null, private_key, scope, null);

client.authorize(function (err, tokens) {
  if (err) {
    return console.log(err);
  }

  getGoogleTitles(client, 'Mark Twain')
  .then(results => console.log(results))
  .catch(error => console.log(error))
});

// Authorize Google api and return results of apiRequest
function getTitles(author) {
  return new Promise((resolve, reject) => {

    client.authorize(function (err, tokens) {
      if (err) {
        return console.log(err);
      }

      let titles = apiRequest(client, author)
      
      if (titles) resolve(titles);
      else reject (err);

    })
  })
}

// Function returns a promise with the books by author
function apiRequest(client, author) {
  return new Promise((resolve, reject) => {

    //
    const books = google.books({ version: 'v1', auth: client });
    const options = {
      key: apiKey,
      langRestrict: 'en',
      maxResults: 5,
      prettyPrint: false,
      download: 'epub',
      filter: 'free-ebooks',
      country:'US',
      fields: 'items(id,volumeInfo/title)',
      q: `inauthor:"${author}"`
    };

    // call the API method and pass options as the first argument
    books.volumes.list(options, (err, titles) => {
      if(err) reject(err);
      else    resolve(titles.items);
    });
  });
}