How to retrieve Session value from JavaScript

In my current project, I am using Visual Studio 2008 and .NET Framework 3.5.
On one of the web pages which use a common master page, I need to retrieve the value of a Session whose value was set by the code behind.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="ViewSubscriptions.aspx.cs" MasterPageFile="~/MSATSMain.master" Inherits="ViewSubscriptions" %>

<asp:Content ID="Content1" ContentPlaceHolderID="Main" runat="server">
    <script type="text/javascript">
        function showConfirm() {
            var exist = '<%= Session("SubscriptionsExist")%>';
            ...
        }
    </sc ...