jQuery newbie: what does jQuery(function($) { … }) means?

Question

I know in jQuery, $(callback) is the same as jQuery(callback) which has the same effect as $(document).ready().

How about

Answer 1

jQuery(function($) {

});

is the safest version of all three. It makes $ the local variable and thus gracefully avoids the conflicts with any other variables which possibly use $ symbol.

I think it was also added fairly recently, don't remember seeing it before.

These function all do the same things - execute some code when DOM is ready. $(document).ready(function(){}) is the original one, and it matches the underlying javascript API.

"$" and "jQuery" which accept function as an arguments were created as shortcuts to avoid repeating such a common construct. Accepting a function which accepts $ as its first argument is a further syntax sugar - now you get convenience of the closures without the need to do it yourself.