What is the purpose of wrapping whole Javascript files in anonymous functions like “(function(){ … })()”?

Question

I have been reading a lot of Javascript lately and I have been noticing that the whole file is wrapped like the following in the .js files to be imported.

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Answer 1

Javascript in a browser only really has a couple of effective scopes: function scope and global scope.

If a variable isn't in function scope, it's in global scope. And global variables are generally bad, so this is a construct to keep a library's variables to itself.