Hi moquamar,

Please refer below Article.

ASP.Net: Get HttpContext.Current.Session value in JavaScript or jQuery

Hi moquamar,

Refer below example.

HTML

C#

Your Name :
<asp:TextBox ID="txtUserName" runat="server"></asp:TextBox>
<input id="btnGet" type="button" value="Get Session" onclick="GetSession()" />
<script type="text/javascript">
    window.onload = function () {
        '<% var MyVar = "123";
            Session["Data"] = MyVar; %>';
    }

    function GetSession() {
        var name = document.getElementById("<%=txtUserName.ClientID%>").value;
        var request;
        if (window.XMLHttpRequest) {
            request = new XMLHttpRequest();
        }
        else if (window.ActiveXObject) {
            request = new ActiveXObject("Microsoft.XMLHTTP");
        }
        if (request != null) {
            var url = "Default.aspx/GetSession";
            request.open("POST", url, false);
            var params = "{name: '" + name + "'}";
            request.setRequestHeader("Content-Type", "application/json");
            request.onreadystatechange = function () {
                if (request.readyState == 4 && request.status == 200) {
                    alert(JSON.parse(request.responseText).d);
                }
            };
            request.send(params);
        }
    }
</script>

VB.Net

Your Name :
<asp:TextBox ID="txtUserName" runat="server"></asp:TextBox>
<input id="btnGet" type="button" value="Get Session" onclick="GetSession()" />
<script type="text/javascript">
    window.onload = function () {
        '<% Dim MyVar = "123"
    Session("Data") = MyVar %>';
    }

    function GetSession() {
        var name = document.getElementById("<%=txtUserName.ClientID%>").value;
        var request;
        if (window.XMLHttpRequest) {
            request = new XMLHttpRequest();
        }
        else if (window.ActiveXObject) {
            request = new ActiveXObject("Microsoft.XMLHTTP");
        }
        if (request != null) {
            var url = "Default.aspx/GetSession";
            request.open("POST", url, false);
            var params = "{name: '" + name + "'}";
            request.setRequestHeader("Content-Type", "application/json");
            request.onreadystatechange = function () {
                if (request.readyState == 4 && request.status == 200) {
                    alert(JSON.parse(request.responseText).d);
                }
            };
            request.send(params);
        }
    }
</script>

Code

C#

[System.Web.Services.WebMethod]
public static string GetSession(string name)
{
    return "Hello " + name + Environment.NewLine + "Session value is : " + HttpContext.Current.Session["Data"];
}

VB.Net

<System.Web.Services.WebMethod>
Public Shared Function GetSession(ByVal name As String) As String
    Return "Hello " & name & Environment.NewLine & "Session value is : " & HttpContext.Current.Session("Data")
End Function

Screenshot