Gather All Google Drive Files of a Certain Type and Change Owner

Code.gs

const newOwner = 'blah@example.com';
const fileTypesToTransfer = ['application/vnd.google-apps.form']; // https://developers.google.com/drive/api/guides/mime-types

function changeOwnership() {

  console.log('Gathering all files in Drive of type ' + fileTypesToTransfer.join(',') + '...');
  
  let fileIterator = DriveApp.searchFiles(fileTypesToTransfer.map(x => 'mimeType = "' + x + '"').join(' or '));
  let files = [];
  while (fileIterator.hasNext()) {
    files.push(fileIterator.next());
  }

  console.log('Transferring ownership of ' + files.length + ' files...');

  for (let file of files) {
    try {
      file.setOwner(newOwner);
    }
    catch(e) {
      console.error('Problem updating ownership for the file ' + file.getName() + '. Continuing...');
    }
    Utilities.sleep(100); // .1 secs, avoiding rate limiting
  }
  
}