Backend Code for Passing Subscriber Key of User to Frontend Page

Backend AmpScript and ServerSide JavaScript
%%[


set @Category_1 = RequestParameter("Category 1")
set @Category_2 = RequestParameter("Category 2")
set @Category_3 = RequestParameter("Category 3")
set @Category_4 = RequestParameter("Category 4")
set @Category_5 = RequestParameter("Category 5")
set @UnsubscribeFromAll = RequestParameter("UnsubAll") 
set @SubscriberKey = RequestParameter("SubKey")
set @currentTime  = Now()

set @data = UpsertData("PreferenceCentre",1,"Subscriberkey", @SubscriberKey, "Category_1", @Category_1, "Category_2", @Category_2, "Category_3", @Category_3, "Category_4", @Category_4, "Category_5", @Category_5, "UnsubscribeFromAll", @UnsubscribeFromAll, "UpdatedDate", @currentTime)

]%%

<meta http-equiv="refresh" content="0; URL='%%=RedirectTo(CONCAT(CloudPagesURL(3109,"SubscriberKey",@SubscriberKey)))=%%'">



<script runat="server">

    Platform.Load("core", "1");

    var api = new Script.Util.WSProxy();

    try {

        var subscriberKey = Variable.GetValue("@SubscriberKey");
        var unsubscribe = Variable.GetValue("@UnsubscribeFromAll");

        if (unsubscribe.toLowerCase() === "true") {
            // Update subscriber status to Unsubscribed
            var updateSubscriber = {
                SubscriberKey: subscriberKey,
                Status: "Unsubscribed"
            };

            var updateResult = api.updateItem("Subscriber", updateSubscriber);

            
        } else {
            // Update subscriber status to Active
            var updateSubscriber = {
                SubscriberKey: subscriberKey,
                Status: "Active"
            };

            var updateResult = api.updateItem("Subscriber", updateSubscriber);

            
        }

    } catch(error) {
        
    } 

</script>