Isn't this because GTM doesn't support ES6?

@ben_mrm You could do this in your activity rather than a profile script using a cookie with an explicit expiration to accomplish this.Basically, in your activity code set or check for the cookie when the experience loads and if it exists do nothing. If the cookie has not been set, then run your pop...

Happy to help!I think you marked your reply as the correct answer. Mind marking my response as the correct answer @salizzi 

+1 Subscribing as well. We have wondered about different ways to accomplish this for as long as I can remember. When multiple teams are working on different aspects of a project obviously communication is key but sometimes changes or updates slip through the cracks and completely wipe tests out. I a...

@Kishore_Kumar_  Thanks for the response, looks like these are the two options. By any chance do you know where in the documentation I would be able to find specifics about the two options? I am not an AEM developer, I work mostly in Target.  Any further assistance is very much appreciated. 

When I run into something specific to the URL pramaters like this, I often use a QA/Debug audience that contains specific Marketing Cloud Visitor IDs including my own and any other individuals that will need to QA the experience. (If you are not sure how to get your MCVID I added instructions at the...