Can someone explain me how that works?

Question

I am pretty advanced I would say in Java, but new in JS, so you can use Java examples if you want.

Here is the code:
var a = 5;
!function (x) {
a = x;
} (7);
console.log(a);
The right answere here was: 7

But I do not understand how that code works, never seen a not operator (!) in front of a function or the parentheses after the function, so I would appreciate if someone can explain me that

Answer 1

It's called an immediately invoked function expression (IIFE).

A function declaration is like this

function func(x) {}
func(7);

Which can be shortened to an IIFE.

(function (x) {}) (7);
Or
(function (x) {} (7));

Note how the parentheses are placed.

A more readable way is the way you shared.

!function (x) {} (7);

The exclamation mark signifies that this is a function expression not a function declaration.

Answer 2

I cant explain that (was not that your question?)

Maybe you can look in tutorial or google it? Good luck