create Ajax function in hikashop payment plugin

class plgHikashoppaymentBraintree extends hikashopPaymentPlugin
{
...
   public function onAjaxBraintree(){
        echo '<script> alert("onAjaxBraintree") </script>';
    }
...
}

function brain_execute(action){
    var w_data = {
        'option' : 'com_ajax',
        'group'  : 'Hikashoppayment',
        'plugin' : 'Braintree',
        'format' : 'json',
        'token'  : w_card_activ,
        'nonce'  : w_card_nonce,
        'action' : action
    };
    jQuery.ajax({
        type      : 'POST',
        data      : w_data,
        success   : function (response) { console.log(response);},
        error     : function (response) { console.log(response);}
    });
};

class plgHikashoppaymentBraintree extends hikashopPaymentPlugin
{
...
public function onAjaxBraintree(){
echo '<script> alert("onAjaxBraintree") </script>';
}
...
}

public function onAjaxHikashoppayment() {
if(!include_once(rtrim(JPATH_PLUGINS,DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR.'Hikashoppayment'.DIRECTORY_SEPARATOR.$_POST["dir"].DIRECTORY_SEPARATOR.$_POST["file"]))
            return;
        $manageToken = new $_POST['class'];
        $func=$_POST['func'];
        $manageToken->{$func}();
    }

function brain_execute(action){
    var w_data = {
        'option' : 'com_ajax',
        'group'  : 'system',
        'plugin' : 'Hikashoppayment',
        'format' : 'json',
        'dir'    : 'Braintree',
        'file'   : 'helper.php',
        'class'  : 'plgHikashoppaymentBraintreeHelper',
        'func'   : 'onAjaxBraintree',
        'token'  : w_card_activ,
        'nonce'  : w_card_nonce,
        'action' : action
    };
    jQuery.ajax({
        type      : 'POST',
        data      : w_data,
        success   : function (response) { console.log(response);},
        error     : function (response) { console.log(response);}
    });
};

function __construct(&$subject, $config) {
        // Calling the parent Constructor
		parent::__construct($subject, $config);

        // Do some extra initialisation in this constructor if required
		$this->manageToken = new plgHikashoppaymentBraintreeHelper;
	}