Mastering JavaScript

Functions, Closures, and Modules
In the bar() function, we are inadvertently modifying the value of i=2. When we
call bar() from within the for loop, the value of the i variable is set to 2 and we
never come out of an infinite loop. This is a bad case of namespace collision.
So far, using functions as a scope sounds like a great way to achieve modularity and
correctness in JavaScript. Well, though this technique works, it's not really ideal.
The first problem is that we must create a named function. If we keep creating such
functions just to introduce the function scope, we pollute the global scope or parent
scope. Additionally, we have to keep calling such functions. This introduces a lot of
boilerplate, which makes the code unreadable over time:
var a = 1;
//Lets introduce a function -scope
//1. Add a named function foo() into the global scope
function foo() {
var a = 2;
console.log( a ); // 2
}
//2. Now call the named function foo()
foo();
console.log( a ); // 1
We introduced the function scope by creating a new function foo() to the global
scope and called this function later to execute the code.
In JavaScript, you can solve both these problems by creating functions that
immediately get executed. Carefully study and type the following example:
var a = 1;
//Lets introduce a function -scope
//1. Add a named function foo() into the global scope
(function foo() {
var a = 2;
console.log( a ); // 2
})(); //