How to call javascript on the click event of a tree node in asp .net

 
<script type="text/javascript">
    function alertVal() {
        alert("Hai");
    }
</script>

 
    protected void Page_Load(object sender, EventArgs e)
    {
        TreeView1.Attributes.Add("onclick", "alertVal()");
 
    }

Source : http://www.codeproject.com/Questions/364132/How-to-call-javascript-on-the-click-event-of-a-tre