Turn a Google Form response into a PDF and email it

/**
 * Turn each Google Form response into a PDF in Drive and email it to the respondent.
 * Trigger: installable "On form submit" trigger on the response spreadsheet for onFormSubmit.
 * The form must collect an email in a question titled "Email".
 */
var FP = { folderId: 'PASTE_FOLDER_ID', emailField: 'Email', title: 'Form response', subject: 'Your copy of your response' };

function escapeHtml_(s) {
  return String(s).replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
}

function onFormSubmit(e) {
  if (!e || !e.namedValues) return 'skip:no-event';
  var rows = Object.keys(e.namedValues).map(function (q) {
    return '<tr><th align="left">' + escapeHtml_(q) + '</th><td>' + escapeHtml_(e.namedValues[q].join(', ')) + '</td></tr>';
  });
  var html = '<h1>' + escapeHtml_(FP.title) + '</h1><table border="1" cellpadding="6">' + rows.join('') + '</table>';
  var stamp = Utilities.formatDate(new Date(), Session.getScriptTimeZone(), 'yyyy-MM-dd HHmm');
  var pdf = Utilities.newBlob(html, 'text/html', FP.title).getAs('application/pdf').setName(FP.title + ' ' + stamp + '.pdf');
  DriveApp.getFolderById(FP.folderId).createFile(pdf);
  var to = e.namedValues[FP.emailField] ? String(e.namedValues[FP.emailField][0]).trim() : '';
  if (!/^[^@\s]+@[^@\s]+\.[^@\s]+$/.test(to)) return 'saved:no-email';
  MailApp.sendEmail({ to: to, subject: FP.subject, body: 'Your response is attached.', attachments: [pdf] });
  return 'saved+sent';
}