Sorry for the delay in my reply. Without having the full source it will be hard to diagnose exactly what the issue is.
You only need to set the static folder to something else in a blueprint if you need it to be different then the main applications static folder.
The way you have it setup right now is a little bit confusing.
Essentially this is where your myJSfile.js should be located for Flask to find it based on your code:
and you are telling flask the url to the file should be/shopify_bp/static/myJSfile.js which im not sure is what you want.
My guess is that it is not locating your static file. Here are a couple links for you to check out on this issue
Seems like my static files aren't being served properly. This is what it looks like right now: myApp __init__.py static…stackoverflow.com
According to the Flask readme, blueprint static files are accessible at blueprintname/static. But for some reason, it…stackoverflow.com
If you need further assistance let me know but it would be really helpful if you could post a bit more of your code as well.
Hope that helps!