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

(function(){
     alert(2 + 2);
 })();

Above is valid syntax because anything passed inside parenthesis is consider as function expression.

function(){
    alert(2 + 2);
}();

Above is not valid syntax. Because java script syntax parser looks for function name after function keyword since it doesn't find anything it throws an error.