Class DataValidation

 // 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);
 textItem.setValidation(textValidation);