Ajax response from controller file Magento 2

To Pass ajax response from the controller in Magento 2, You need to use Magento\Framework\Controller\Result\JsonFactory Object.

Magento\Framework\Controller\Result\JsonFactory used for sending a response from a controller to ajax request.

Pass your response in setData() method.

namespace Rbj\AjaxResponse\Controller\Index;

class AjaxResponse extends \Magento\Framework\App\Action\Action
	public function __construct(
	    \Magento\Framework\App\Action\Context $context,
	    \Magento\Framework\Controller\Result\JsonFactory $resultJsonFactory
	) {
	    $this->resultJsonFactory = $resultJsonFactory;

 public function execute()
        $resultJson = $this->resultJsonFactory->create();
        $htmlContent = 'Pass Html Content';
        $success = true;
        return $resultJson->setData([
            'html' => $htmlContent,
            'success' => $success

From Js/Template file which place you have called Ajax Call, You can get Response as html and success parameter from an above response.

You can manage your Response from controller file.