jqTree - collapse/expand tree

jqtree.js

var $tree = $('#tree1');
$('#collapse').click(function() {
  var tree = $tree.tree('getTree');
  tree.iterate(function(node) {

    if (node.hasChildren()) {
      $tree.tree('closeNode', node, true);
    }
    return true;
  });
});

$('#expand').click(function() {
  var tree = $tree.tree('getTree');
  tree.iterate(function(node) {

    if (node.hasChildren()) {
      $tree.tree('openNode', node, true);
    }
    return true;
  });
});