Downloads a directory structure from Google Drive. Also handles exporting of the Google Docs.

download-from-google-drive.js

const fs = require('fs-extra');
const google = require('googleapis');
const OAuth2 = google.auth.OAuth2;
const key = require('./key.json');

var baseFolder = 'base';

function downloadFile(file, path) {
  setTimeout(function () {
        var filePath = path.concat(file.name).join('/');
        console.log('creating file: ', filePath);
        var dest = fs.createWriteStream(filePath);

        // For Google Docs files only
        drive.files.get({
           fileId: file.id,
           alt: 'media'
        })
        .on('end', function() {
            console.log('Done');
        })
        .on('error', function(err) {
            console.log('Error during download', err);
        })
        .pipe(dest);
    }, 1000);
}

function exportFile(file, path, mimeType, suffix) {
  setTimeout(function () {
        var name = file.name + suffix;
        var filePath = path.concat(name).join('/');
        console.log('exporting to file: ', filePath);
        var dest = fs.createWriteStream(filePath);

        // For Google Docs files only
        drive.files.export({
           fileId: file.id,
           mimeType: mimeType
        }, {
          encoding: null // Make sure we get the binary data
        })
        .on('end', function() {
            console.log('Done');
        })
        .on('error', function(err) {
            console.log('Error during download', err);
        })
        .pipe(dest);
    }, 1000);
}


function visitDirectory(fileId, parentPath) {
  console.log('path: ', parentPath.join('/'));

  setTimeout(function () {
      drive.files.list({
         includeRemoved: false,
         spaces: 'drive',
         fileId: fileId,
         fields: 'nextPageToken, files(id, name, parents, mimeType, modifiedTime)',
         q: `'${fileId}' in parents`
      }, function (err, resp) {
        if (!err) {
            var i;
            var files = resp.files;
            for (i=0; i<files.length; i++) {
                if (files[i].mimeType == 'application/vnd.google-apps.folder') {
                    console.log('directory: ' + files[i].name);
                    var path = parentPath.concat(files[i].name);
                    visitDirectory(files[i].id, path);
                     try {
                        fs.mkdirp( parentPath.concat(files[i].name).join('/'));
                     } catch (err) {
                        // Ignored
                     }
                } else if (files[i].mimeType === 'application/vnd.google-apps.document') {
                    exportFile(files[i], parentPath, 'application/pdf', '.pdf');
                } else if (files[i].mimeType === 'application/vnd.google-apps.spreadsheet') {
                    // exportFile(files[i], parentPath, 'text/csv, '.csv');
                    exportFile(files[i], parentPath, 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', 'xlsx');
                } else if (files[i].mimeType.startsWith('application/vnd.google-apps')) {
                    console.log('unhandled Google Doc type: ', files[i].mimeType);
                } else {
                    console.log('unhandled type: ', files[i].mimeType);
                    downloadFile(files[i], parentPath);
                }
            }
        } else {
            console.log('error: ', err);
        }
      });
  }, 1000);
}


var jwtClient = new google.auth.JWT(
  key.client_email,
  null,
  key.private_key,
  ['https://www.googleapis.com/auth/drive.readonly'],
  null
);

const drive = google.drive({
  version: 'v3',
  auth: jwtClient
});

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

  var fileId = 'xxxxx';

  visitDirectory(fileId, [baseFolder]);

});

// ref: https://developers.google.com/drive/v3/web/folder
// ref: https://www.npmjs.com/package/googleapis
// ref: https://developers.google.com/drive/v3/web/search-parameters
// ref: https://developers.google.com/drive/v3/web/manage-downloads
// ref: https://developers.google.com/drive/v3/reference/files#resource