Jsom get host subsites list

I have following code to get list of subsites on the hostweb, but it returns titles for all objects including lists, how can I filter that it only return subsite titles? Thanks

hostUrl = decodeURIComponent(getQueryStringParameter("SPHostUrl"));
hostContext = new SP.AppContextSite(clientContext, hostUrl);
hostWeb = hostContext.get_web();
hostSubSites = hostWeb.get_webs();

clientContext.load(hostSubSites);
clientContext.executeQueryAsync(onGetSubSiteSuccess, onGetSubSiteFail);


 var subs = hostSubSites.getEnumerator();
    var subSite;
    var subTitles = " ";
    while (subs.moveNext()) {
        subSite = subs.get_current();
        subTitles += subSite.get_title()+"<br/> ";
    }

    $('#allSites').html(subTitles);