jQuery, REAL :not operator equivalent?

this code line select all the children inputs inside any div who his class name is not "id" and "quantity" ::

$("div.item > div:not(.id,.quantity) > :input").live("keydown",function(event) {});

what is the code line to do the opposite?, something like ::

$("div.item > div:filter(.id,.quantity) > :input").live("keydown",function(event) {});

( of course :filter is not a valid jQuery selector )

I don't know if I would recommend this, but you can use :not twice:

$("div.item > div:not(:not(.id,.quantity)) > :input")

http://jsfiddle.net/6aW2B/

A better way is to create your own :is selector

$.expr[':'].is = function(elem, index, match){
    return $(elem).is(match[3]);
};

$("div.item > div:is(.id,.quantity) > :input")

http://jsfiddle.net/8Uny2/

I presume you are thinking of an "or" concept. Unfortunately, this doesn't really exist in jQuery/CSS selection. You need to do an "or" for the whole selection:

$('div.item > div.id > :input, div.item > div.quantity > :input')

If you are not using live, the easiest way to do this is with DOM traversal:

$('div.item').children('div.id, div.quantity').children(':input')

Since you are using live, the first example is probably the simplest technique.