javascript how to get the web page get Session variable

Question

I'm trying to use a Session variable in javascript.

I have tried a number of post suggestions without success unfortinately.

I see this example all over the place.

    var userName = '<%= Session["UserName"] %>'

However that is not working, at least for me. What I am trying to do is as below.

    var qrdataString = "<qr-code data=" + "XL" + ' <%= Session["style"] %>'  + "></qr-code>";
    document.getElementById("styleqr").innerHTML = qrdataString; 

Using Single quotes where they appear above just returns the string as

    <%=Session["xUID"]%>   in the alert that I use to show me the returned value

Using Double quotes give me either - unexpected token: string literal - or unexpected token identifier.

Thanks