self executing function jquery vs javascript difference

Question

What are the difference among -

First :-

(function () {

    var Book = \'hello\';

}());

Second:-

Answer 1

Immediately-invoked function expressions (IIFE) is one of the core JavaScript features. Its main aim is not to clutter the namespaces with disposable functions and variables.

if you use a variable or a function only once, you don't need to make it available for the rest of the code (therefore you make a private access, for example). In case of functions, you may just let them be anonymous, just like the following:

(function(){
  console.log("Hello symfony world!");
}());

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