fetching webs property

I am a beginner in sharepoint development, if you can help me I did a code below to retrieve all the webs of a web and I want to fetch n these webs and display just those who have some property because they were was provisioned with apps and just want to retrieve these webs but I just can not thank you for your reading.

 var context = SP.ClientContext.get_current();

 var webs = context.get_web().get_webs();
 context.load(webs);
 context.executeQueryAsync(function(sender, args) {
 var webEnum = webs.getEnumerator();
   while(webEnum.moveNext()){
 var web = webEnum.get_current();
   alert(web.get_title());
   }
 }, function(){alert('err');});