js取treeview checkbox 选中值

protected void Page_Load(object sender, EventArgs e)

        {

            if (!Page.IsPostBack)

            {

               

            TreeView3.Attributes.Add("onclick", "OnTreeNodeChecked('" + TreeView3.ID + "'," + TreeView3.ClientID + ")"); 





        }

function OnTreeNodeChecked(controlID,obj) 

{

    tree=obj;



    var ele = event.srcElement; 

    if(ele.type=='checkbox'&& ele.checked) 

    { 

    

       这边如何取得checkbox选中时的值    } 

}