$.ajax({
    url: Joomla.getOptions('system.paths').base+'/index.php?option=mypage&view=cartcheckout&task=cartcheckout_autoSave&tmpl=component&stepId='+stepId,
    type: 'POST',
    //async:false,
    data:values,
    dataType: 'json',

    success: function(response)
    {
        // do something
    },
    error: function(response)
    {
        // show ckout error msg
        console.log(' ERROR!!' );
        return e.preventDefault();
    }
});

Joomla.getOptions('system.paths').base+'/index.php?option=mypage&view=cartcheckout&task=cartcheckout_autoSave&tmpl=component&stepId='+stepId

url:'/index.php?option=com_mypage&view=cartcheckout&task=cartcheckout_autoSave&tmpl=component&stepId='+stepId,