JavaScript function with 'undefined' parameter

Question

Going around Modernizr source code I have found strange thing:

window.Modernizr = (function(window,document,undefined) {

After that this function will be called with two arguments (this, this.document).

Why undefined is used here? Is it meaningful or it's just strange code-style?

I know that this construction is overriding undefined in function context, but I can't understand for what. — Gleb M Borisov, Jan 10 '11 at 19:07

score 23 · Accepted Answer · answered Jan 10 '11 at 19:06

23

Creates a local undefined in case someone redefines undefined somewhere in the scope chain.

Also provides a faster lookup since undefined is a global property, so the scope chain traversal is reduced.

answered Jan 10 '11 at 19:06

user113716

1

Wow, thanks for fast answer. I don't think about that. – Gleb M Borisov Jan 10 '11 at 19:08
7

Yes, I believe Paul Irish refers to that as the asshole effect in the 10 things I learned about JQuery video. – Loktar Jan 10 '11 at 19:10

1 Answers1