CaptchaCode = 
{
    replaceCaptchaImage: function (oldPublicCode, form)
    {
        ajax.set("onSuccess", function(ajaxObj)
        {
            var response = ajaxObj.parseJSON();
            var newPublicCode = response.newPublicCode;
            $('captchaImage').src = setting.siteRootUrl + '/index.php/captcha/png/' + response.newPublicCode;
            form.publicCode.value = newPublicCode; 
        })                                  
        .post('/captcha/change/' + oldPublicCode);    
    }
}