Why can't I access my jQuery collection once it has been used to wrap another element?

Look at this code:

var b = $('<div id="b" />');
$('#a').wrap(b);
b.css({ border: '5px solid red' });

jsFiddle.

The element stored under b will not have a border.

Is there any way to access b still once it has been used to wrap anoth开发者_如何学运维er element?

Or should I do b = $('#b') again?

I don't think jQuery actually uses the same instance of "b" to wrap it. You would need to overwrite "b" with the one that was created to do the wrap.

var b = $('<div id="b" />');

b = $('#a').wrap(b).parent();

b.css({ border: '5px solid red' });

I suppose the reason is that if a was a class instead of an ID, and there were several of them, you wouldn't be able to use the same element to individually wrap each .a.

So it must make a clone of b that it uses to do the wrap.

var b = $('');

$('#a').wrap(b).css({ border: '5px solid red' });

The b contain the element in memory, after DOM append, you send b to DOM at second line and before call css() by the element referenced by "b" and not by the DOM match.