code: function(tree, initLevel, toLevel, action) {
      if (initLevel <= toLevel) {
        action(tree, initLevel);
        if(!tree.children) return;
        for ( var i = 0, ch = tree.children; i < ch.length; i++) {
          this.eachLevel(ch[i], initLevel + 1, toLevel, action);
        }
      }
    }
docs: /*
  Method: eachLevel
  
  Iterates on tree nodes with relative depth less or equal than a specified level.
  
  Parameters:
  
  tree - (object) A JSON tree or subtree. See also <Loader.loadJSON>.
  initLevel - (number) An integer specifying the initial relative level. Usually zero.
  toLevel - (number) An integer specifying a top level. This method will iterate only through nodes with depth less than or equal this number.
  action - (function) A function that receives a node and an integer specifying the actual level of the node.
  
  Example:
  (start code js)
  $jit.json.eachLevel(tree, 0, 3, function(node, depth) {
  alert(node.name + ' ' + depth);
  });
  (end code)