How do you make the right area of visibility?

[elysha]

In the Jquery library, there is a single feature that the code fragment takes an anonymous variable and is transmitted as an argument of function.

$(function(){ ///... })

The question is... How did they do that? I made the following fragment:

function Lib(func){
  var a = 12;
  return func();
}
Lib(function(){ console.log(a); });

But variable a Not in the field of visibility... How to make the anonymous function a variable a and in general all methods and characteristics of the function Lib♪ I wanted to set up a set of functions (to be accessible only internally) Lib

 Lib(function(){ console.log(a); });

I understand there's another option for implementation, but it's the jQuery style.

[courtlanda]

function Lib(func){
  var a = 12;
  return func(a);
}

Lib(function(a){ console.log(a); });