I know in jQuery, $(callback) is the same as jQuery(callback) which has the same effect as $(document).ready().
How about
jQuery(function($) {
});
Can some one explain to me what does this kind of function mean?
What does it do?
what is the difference between this one and $(callback)??
what is the difference between this one and $(function())??
jQuery(function($) {
});
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.