SetField() for Webstore Cart Messaging is not Working for Clientside javascript

The SetField function is a server-side script. As such, it is not able to grab a variable on the client side browser. The SetField only triggers when the page loads, and so if the setField function is called after the page loads with JavaScript, it is not going to work.

This is similar to the getCurrentAttribute website tag in the sense that it only displays upon page load and it cannot be used to get dynamic data.