how to save session value in javascript code example

Example 1: how to get session value using javascript

sessionStorage.getItem("SessionName")

Example 2: set a value in session using javascript

<script type="text/javascript">
function SetUserName()
{
    var userName = "Shahid Bhat";
    '<%Session["UserName"] = "' + userName + '"; %>';
     alert('<%=Session["UserName"] %>');
}
</script>