How does this JavaScript/jQuery syntax work: (function( window, undefined ) { })(window)?

Question

Have you ever taken a look under the hood at the jQuery 1.4 source code and noticed how it\'s encapsulated in the following way:

(function(          


        

Answer 1

Tested with 1000000 iterations. This kind of localization had no effect in performance. Not even a single millisecond in 1000000 iterations. This is simply useless.