Function scopes and global variables

Question

var foo = '1',
    bar = '2';

console.log(foo, bar, window.foo); //1, 2, undefined

(function(foo){
    console.log(foo, bar); //2, 2
})(bar);

I have two trivial questions regarding the code above:

1. Why is window.foo undefined? Aren't all global variables attached to the window object by default?

2. Why is foo ===2 inside of the closure? I know that I'm passing the original bar with the alias foo, which is 2, but outside of the function scope foo is still 1. And as far as I know, the original foo can be accessed from inside of the closure as well. Is the "new foo" prioritized since it's passed as an argument to the IIFE?

http://jsfiddle.net/GbeDX/

Answer 1

Why is window.foo undefined? Ins't all "global" variables automatically attached to the window object?

Yes, global variables become properties of window, but the code is not run in global scope in your fiddle. It is run in the load event handler (see the second checkbox on the left hand side, it says "onLoad"). Here it is run in global scope: http://jsfiddle.net/GbeDX/1/

Why is foo === 2 inside of the closure? [...] And as far as I know, the original foo can be accessed from inside of the closure as well.

No, it can't. The parameter foo shadows the variable foo. If it is a global variable though, you can access it with window.foo.