code: function createTree( data, node ) {
  
      if (Object.keys(data).length > 0) {
  
        var sec = document.createElement("ul");
        node.appendChild( sec );
  
        for (var k in data) {
          var li = document.createElement("li");
          li.innerHTML = k;
          sec.appendChild( li );
          createTree( data[k], li );
        }
      }
    }
docs: Build menu