Solved
Is "use strict" required to be in every java script file in AEM?
The purpose of "use strict" is to indicate that the code should be executed in "strict mode". With strict mode you can not use undeclared variables.
My question is, do we need to have this in every piece of custom Javascript file? Can it be set at global level or can we ask AEM to use "use strict" for all Javascript files at global or instance level?
(function($,document) {
"use strict";
...
})(Granite.$, document);