Explain the encapsulated anonymous function syntax

Question

Summary

Can you explain the reasoning behind the syntax for encapsulated anonymous functions in JavaScript? Why does this work: (function(){})(); but

Answer 1

You can also use it like:

! function() { console.log('yeah') }()

or

!! function() { console.log('yeah') }()

! - negation op converts the fn definition to fn expression, therefore, you can invoke it immediately with (). Same as using 0,fn def or void fn def