// prepare the form when the DOM is ready 
$(document).ready(function() { 
    var options = { 
        target:        '#comment_list',   // target element(s) to be updated with server response 
        beforeSubmit:  validate ,   // pre-submit callback 
        clearForm: true,        // clear all form fields after successful submit 
        resetForm: true        // reset the form after successful submit 
    }; 

   $('#commentForm').submit(function() { 
        $(this).ajaxSubmit(options); 
        return false; 
    });

}); 
 
// pre-submit callback 
function validate(formData, jqForm, options) { 
	
      for (var i=0; i < formData.length; i++) { 
			if (!formData[i].value) { 
				alert('กรุณากรอกข้อมูลให้ครบทุกช่อง'); 
				return false; 
			} 
		} 

			return true; 
	}