google/instant-hangouts — pull request #2 by zenorocha (2014-01-25 22:56:41+00:00)
Title: Add `window`, `document` and `undefined` variables to the immediately-invoked function expression

`undefined` is used here as the undefined global variable in ECMAScript 3 is mutable (ie. it can be changed by someone else). `undefined` isn't really being passed in so we can ensure the value of it is truly undefined. In ES5, `undefined` can no longer be modified.

`window` and `document` are passed through as local variable rather than global as this (slightly) quickens the resolution process and can be more efficiently minified.

* http://stackoverflow.com/questions/15777519/using-window-document-and-undefined-as-arguments-in-anonymous-function-th
* http://stackoverflow.com/questions/15030334/jquery-scripts-functionwindow-document-undefined-vs-function-window-d
* http://hughajwood.wordpress.com/2012/09/12/nothing-is-iffy-with-iife-in-javascript/