How does this construct work in JavaScript?

Question

JavaScript

Hello!
Please explain in simple terms.
How does this construct work in JavaScript?

var module = (function (obj) {	
  //code
})(module || {});

I'm completely confused. Thank you.

Answer 1

So it will be more clear?

function f(obj){
  //code
}
var module = f(f() || {});

Answer 2

Design Pattern Module