set a value in session using javascript

1sessionStorage.getItem("SessionName")

1BY LOVE
2sessionStorage.setItem("SessionName", "SessionValue");

1<script type="text/javascript">
2    function GetUserName()
3    {
4
5        var username = '<%= Session["UserName"] %>';
6        alert(username );
7    }
8</script>

1<script type="text/javascript">
2function SetUserName()
3{
4    var userName = "Shahid Bhat";
5    '<%Session["UserName"] = "' + userName + '"; %>';
6     alert('<%=Session["UserName"] %>');
7}
8</script>