d3 force collapsible layout - start page with all nodes collapsed

Question

I just need a simple modification of the layout available here http://mbostock.github.io/d3/talk/20111116/force-collapsible.html

The above visualization starts with

Answer 1

       just do it like this 
        d3.json("json/results.json", function(json) {
               root = json;
               root.x0 = h / 2;
                root.y0 = 0;

                function toggleAll(d) {
                   if (d.children) {
                   d.children.forEach(toggleAll);
                  toggle(d);
                   }
               }

                 root.children.forEach(toggleAll);

                  toggle(root);
                update(root);
                 });