Transfer Google Files Between Accounts

transferFiles.appscript

function start() {
  // Create a folder in your source and destination accounts called "To Copy" and put any document you want copied in there.  
  // Update the code below with the id of that folder
  var copySource = DriveApp.getFolderById('id of source To Copy folder');
  var copyDestination = DriveApp.getFolderById('id of destination To Copy folder');
  
  // Create a folder in your source and destination accounts called "To Move" and put any document you want moved in there.  
  // Update the code below with the id of that folder
  var moveSource = DriveApp.getFolderById('id of source To Move folder');
  var moveDestination = DriveApp.getFolderById('id of destination To Move folder');

  transferFolder(copySource, copyDestination, false);
  transferFolder(moveSource, moveDestination, true);
}

function transferFolder(source, target, doMove) {

  var folders = source.getFolders();
  var files   = source.getFiles();

  while(files.hasNext()) {
    var file = files.next();
    var dest = target.getFilesByName(file.getName());
    if (dest.hasNext()) {
      // skip because file exists
      Logger.log('skipping copy for ' + file.getName() + ' because it exists.');
      continue;
    }

    if (doMove) {
      Logger.log("Moving file: " + file.getName());
      file.moveTo(target);
    } else {
      Logger.log("Copying file: " + file.getName());
      file.makeCopy(file.getName(), target);
    }
  }

  while(folders.hasNext()) {
    var subFolder = folders.next();
    var folderName = subFolder.getName();

    var dest = target.getFoldersByName(folderName);
    var targetFolder;
    if (!dest.hasNext()) {
      Logger.log('creating folder ' + folderName);
      targetFolder = target.createFolder(folderName);
    } else {
      targetFolder = dest.next();
    }
    
    transferFolder(subFolder, targetFolder, doMove);
  }  

}