loader.js:41 Uncaught TypeError: url.match is not a function, When running AJAX in admin form

Question

i have a select field set that triggered AJAX script when onchange, the ajax is calling the controller with post data, but i got an error saying

loader.js:41 Uncaught TypeError: url.match is not a function

here's the code:

$k = Mage::getSingleton('core/session')->getFormKey();
$event = $fieldset->addField(
            'category_id',
            'select',
            array(
                'label'  => Mage::helper('test_sellercenter')->__('Category '),
                'name'   => 'category',
                'values' => Mage::helper('test_sellercenter/dropdown')->getLazadaCategories(),
                'class' => 'required-entry lazadacat',
                'onchange'  => 'checkSelectedItem(this)',
                'container_id' => 'categoryId'
        ));

        $event->setAfterElementHtml("<script type=\"text/javascript\">
          function checkSelectedItem(selectElement){
              new Ajax.Request({
                url: '".$this->getUrl('test_sellercenter/Adminhtml_MassActions/attributeslazada')."',
                type: 'POST',
                data: {category: selectElement.value, form_key:'".$k."'},
                success: function(data) {
                          console.log(data);
                        }
              });

          }
      </script>");

Answer 1

My AJAX function is a mess, i fix the ajax and it runs well now

here's the AJAX code:

$event->setAfterElementHtml("<script type=\"text/javascript\">
          function checkSelectedItem(selectElement){
              var url = '". $this->getUrl('test_sellercenter/Adminhtml_MassActions/attributeslazada')."';
              var category = selectElement.value;
              new Ajax.Request(url, {
                parameters: {isAjax: 1, method: 'POST', data1:category},
                onSuccess: function(data) {
                   if(data.responseText != 'Failed'){
                     console.log(data.responseText);
                   }
                }
              });
          }
      </script>");