Modules not Globals
Often newer JS developers ask when they should turn something into a standalone module. When should that function turn into its own file? There are lots of things we could talk about with componentized architecture. But there is a single thing that should be a massive flashing sign that you need a module.
That thing is global variables. Anytime you touch window. or global. or some other shared variable scope.
Next time you are trying to share things through a global scope... grab a module that you can require into many modules. Usually these wrappers are incredibly light, and they will make your code much cleaner.