Google Apps Script for building a backup of a folder, from Google Drive to Dropbox, every night

drive-to-dropbox.gs

// To store personal documents that really matter (such as tax reports, bank terms,
// employment conditions...) you should opt for a cloud storage (Dropbox, Google Drive...).
// Even if famous SaaS services might be safe enough to not make backups by ourselves, it
// may be even safer to not rely on them and setup this short script for copying a Drive folder
// into Dropbox.

// To generate a Dropbox access token, please follow this guide: http://99rabbits.com/get-dropbox-access-token/

// Don't forget to setup a cronjob:
// 1- Click on 'Edit' menu > 'Current project's triggers'
// 2- Click on 'No triggers set up. Click here to add one now.'
// 3- Select the 'main' function in the 'run' column
// 4- Setup a daily cron at '4am to 5am'
// 5- Click on 'notifications'
// 6- Request daily notifications at 5am
// 7- Click on 'Save' twice
// 8- Enjoy \o/

var driveFolderId = 'changeme';
var dropboxAccessToken = 'changeme';

function buildArchive() {
  var folder = DriveApp.getFolderById(driveFolderId);
  var zipFileName = folder.getName()+'.zip';
  var zipped = Utilities.zip(getBlobs(folder, ''), zipFileName);
  return zipped;
}

// https://stackoverflow.com/a/28018270
function getBlobs(rootFolder, path) {
  var blobs = [];
  var names = {};
  var files = rootFolder.getFiles();
  while (files.hasNext()) {
    var file = files.next().getBlob();
    var n = file.getName();
    while(names[n]) { n = '_' + n }
    names[n] = true;
    blobs.push(file.setName(path+n));
  }
  names = {};
  var folders = rootFolder.getFolders();
  while (folders.hasNext()) {
    var folder = folders.next();
    var n = folder.getName();
    while(names[n]) { n = '_' + n }
    names[n] = true;
    var fPath = path+n+'/';
    blobs.push(Utilities.newBlob([]).setName(fPath)); //comment/uncomment this line to skip/include empty folders
    blobs = blobs.concat(getBlobs(folder, fPath));
  }
  return blobs;
}

function sendArchiveToDropbox(blob) {
  var args = {
    'path': '/' + blob.getName(),
    'mode': {
      ".tag":"overwrite",
    },
    "autorename": true,
    "mute":true,
  };
  
  var options = {
    'method' : 'post',
    'payload' : blob.getBytes(),
    'contentType': 'application/octet-stream',
    'headers': {
      'Authorization': 'Bearer ' + dropboxAccessToken,
      'Content-Type': blob.getContentType(),
      'Dropbox-API-Arg': JSON.stringify(args),
    },
  };
  UrlFetchApp.fetch('https://content.dropboxapi.com/2/files/upload', options);
}

function main() {
  var archive = buildArchive();
  sendArchiveToDropbox(archive);
}

If you reach 6min timeout, you probably need to backup subdirectories separately :-(