drive-sample.js: create and update a file on Google Drive in Node.js

drive-sample.js

// Sample Node.js code to create and update the file on Google Drive.
// Pre-requisites:
// 1. Install Node.js
// 2. $ npm install express open googleapis
// 3. Put the JSON API key into ./key.json
// Usage:
// node drive-sample.js

const express = require('express');
const open = require('open');
const {google} = require('googleapis');

const PORT = 3000; // for a local HTTP server for OAuth2 workflow
const key = require('./key.json'); // JSON API key file

// Main code here
async function createFile(drive, filename) {
  const {data} = await drive.files.create({
    resource: {
      name: filename
    },
    media: {
      mimeType: 'text/plain',
      body: 'initial content'
    },
    fields: 'id'
  });
  return data.id;
}

async function writeCurrentTimeToFile(drive, fileId) {
  const {data} = await drive.files.update({
    fileId,
    media: {
      mimeType: 'text/plain',
      body: new Date().toString()
    },
  });
}

async function main() {
  const scope = ['https://www.googleapis.com/auth/drive.file'];
  const oauth2client = await authenticate(scope);
  console.log('Authenticated');
  const drive = google.drive({
    version: 'v3',
    auth: oauth2client
  });
  const fileId = await createFile(drive, 'time.txt');
  console.log(`Created file with ID ${fileId}`);
  await writeCurrentTimeToFile(drive, fileId);
  console.log(`Updated the file`);
}

main().catch(console.error);

// OAuth2 workflow is a little bit painful
async function authenticate(scope) {
  function waitForCode(url) {
    return new Promise( (resolve, reject) => {
      const expressApp = express();
      const server = expressApp.listen(PORT);
      console.log('Server is listening, go to your browser window to continue...');
      expressApp.get('/oauth2callback', (req, res) => {
        const code = req.query.code;
        if (code === undefined) {
          reject(new Error('Undefined code'));
          return;
        }
        res.send(`OK! We've got OAuth2 code. Now please go back to your application.`);
        console.log('Server is stopping.');
        server.close();
        resolve(code);
      });
    });
  }

  const oauth2client = new google.auth.OAuth2(
    key.installed.client_id,
    key.installed.client_secret,
    `http://localhost:${PORT}/oauth2callback`
  );
  const authorizeUrl = oauth2client.generateAuthUrl({
    access_type: 'offline',
    scope
  });
  open(authorizeUrl);
  const code = await waitForCode();
  const getTokenResponse = await oauth2client.getToken(code);
  oauth2client.setCredentials(getTokenResponse.tokens);
  return oauth2client;
}