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.

(f         


        

Answer 1

That's called a closure. It basically seals the code inside the function so that other libraries don't interfere with it. It's similar to creating a namespace in compiled languages.

Example. Suppose I write:

(function() {

    var x = 2;

    // do stuff with x

})();

Now other libraries cannot access the variable x I created to use in my library.