Javascript w2ui objects - can't get type

Question

I got list of w2ui object on my page. Structure look like that

And part of what inside I want to get only those, which one is type of 'w2layout'.

I use JQuery each to go through like that

jQuery.each(w2ui, 
     function(key, value) {
        console.log(value);
      }
);

But I can't get the left part!

I tried typeof (returns object), and value.constructor (returns object too), tried use instanceof w2layout but without success.

JSON.stringify(value); throws error Converting circular structure to JSON So how can I get this?