Not running nodejs 16+ which supports much of ES2021+? then STOP you can't use this class! It contains both private fields and methods and is written with esm modules. You might be able to transpile it but that is not supported nor encouraged.
To allow and object to have reactivity similar to vue and react without those packages and thus with any nodejs code. This a "backend" app could maintain app settings and allow non vue/react "clients" to get updated values when the app changes state. Essentially this class will create instances of 'mini' state event bus.
The class maintain a private `rx` field. When an object (i.e. property) of the class is made reactive it is converted into a getter/setter (much like vue) and it's actual value is stored within the private rx field. One can access the value of that propery like before but