Class TextValidation

// Add a text item to a form and require it to be a number within a range.
var textItem = form.addTextItem().setTitle('Pick a number between 1 and 100?');
var textValidation = FormApp.createTextValidation()
  .setHelpText('Input was not a number between 1 and 100.')
  .requireNumberBetween(1, 100)
  .build();
textItem.setValidation(textValidation);