Question

So currently I use simple try once:

$.getJSON("server.json", function(data) {
        servicesList.render(data);
});

I wonder how to try until success each 0.5 seconds?

Answer 1

function getFromServer(){
  $.getJSON("server.json", function(data) {
          // Verify your data, if it's not you want run error function 
          if(!data){ onerror(); return; }
          servicesList.render(data);
  }).error(function() { onerror(); });
}

// if error ,run it again.
function onerror(){
    setTimeout(function(){getFromServer();},500);
}

you can find the $.getJSON API help with this link:
http://api.jquery.com/jQuery.getJSON/