trotzig/diffux

define([
    "../../core",
    "../../selector"
    // css is assumed
], function( jQuery ) {

    return function( elem, el ) {
        // isHidden might be called from jQuery#filter function;
        // in that case, element will be second argument
        elem = el || elem;
        return jQuery.css( elem, "display" ) === "none" || !jQuery.contains( elem.ownerDocument, elem );
    };
});