(Function () {}) () usage and advantages _ javascript skills

(Function () {}) () usage and advantages in google's ad js, found such a statement
// I used alert ("test") to replace the statements in it.

(Function () {alert ("test ")})()
Tested, similar to directly executing

Alert ("test ")
So what are the advantages of this usage? Let's talk about it!

Function xx (){...}
Equivalent
Var xx;
Xx = function (){...}

Function () {...} returns a Function object.
(Function object) () is to call this Function

The intuitive advantage is that several statements that need to be executed in sequence are organized into a unit, so that the logic is clear and there is no need to name them.
Possible for saving: The anonymous function is like a temporary variable and can be destroyed immediately after execution.