Judge whether the node is the parent node.
1. When zTree initialize the node data, the node which has children is set to true, otherwise false.
2. When zTree initialize the node data, if set treeNode.isParent to true, the node will be set to be parent node.
3. In order to solve the problem of someone make json data, supporting "false", "true" format of the data string.
true means: the node is parent node.
false means: the node is not parent node.
var treeObj = $.fn.zTree.getZTreeObj("tree");
var sNodes = treeObj.getSelectedNodes();
if (sNodes.length > 0) {
var isParent = sNodes[0].isParent;
}