How to get Tree view selected node value using Javascript

<asp:treeview id="TreeView1" runat="server" xmlns:asp="#unknown">
    <SelectedNodeStyle ForeColor="Black" />
</asp:treeview>
<asp:button id="Button1" runat="server" text="GetSelectedNode" onclientclick="return GetSelectedNode();" xmlns:asp="#unknown" />

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        TreeView1.Nodes.Add(new TreeNode("Mango", "Fruit1"));
        TreeView1.Nodes.Add(new TreeNode("Apple", "Fruit2"));
        TreeView1.Nodes.Add(new TreeNode("Pineapple", "Fruit3"));
        TreeView1.Nodes.Add(new TreeNode("Orange", "Fruit4"));
        TreeView1.Nodes.Add(new TreeNode("Grapes", "Fruit5"));
    }
}

<script type="text/javascript">
function GetSelectedNode() {
    var treeViewData = window["<%=TreeView1.ClientID%>" + "_Data"];
    if (treeViewData.selectedNodeID.value != "") {
        var selectedNode = document.getElementById(treeViewData.selectedNodeID.value);
        var value = selectedNode.href.substring(selectedNode.href.indexOf(",") + 3, selectedNode.href.length - 2);
        var text = selectedNode.innerHTML;
        alert("Text: " + text + "\r\n" + "Value: " + value);
    } else {
        alert("No node selected.")
    }
    return false;
}
</script>