jquery/src/traversing.js

var winnow = function( elements, qualifier, keep ) {
	if(jQuery.isFunction( qualifier )) {
		return jQuery.grep(elements, function(elem, i) {
			return !!qualifier.call( elem, i ) === keep;
		});
	} else if( qualifier.nodeType ) {
		return jQuery.grep(elements, function(elem, i) {
			return (elem === qualifier) === keep;
		})
	} else if( typeof qualifier === "string" ) {
		var filtered = jQuery.grep(elements, function(elem) { return elem.nodeType === 1 });

		if(isSimple.test( qualifier )) return jQuery.multiFilter(qualifier, filtered, !keep);
		else qualifier = jQuery.multiFilter( qualifier, elements );
	}

	return jQuery.grep(elements, function(elem, i) {
		return (jQuery.inArray( elem, qualifier ) >= 0) === keep;
	});
}

jQuery.fn.extend({
	find: function( selector ) {
		var ret = this.pushStack( "", "find", selector ), length = 0;

		for ( var i = 0, l = this.length; i < l; i++ ) {
			length = ret.length;
			jQuery.find( selector, this[i], ret );

			if ( i > 0 ) {
				// Make sure that the results are unique
				for ( var n = length; n < ret.length; n++ ) {
					for ( var r = 0; r < length; r++ ) {
						if ( ret[r] === ret[n] ) {
							ret.splice(n--, 1);
							break;
						}
					}
				}
			}
		}

		return ret;
	},

	not: function( selector ) {
		return this.pushStack( winnow(this, selector, false), "not", selector);
	},

	filter: function( selector ) {
		return this.pushStack( winnow(this, selector, true), "filter", selector );
	},

	closest: function( selector, context ) {
		var pos = jQuery.expr.match.POS.test( selector ) ? jQuery(selector) : null,
			closer = 0;

		return this.map(function(){
			var cur = this;
			while ( cur && cur.ownerDocument && cur !== context ) {
				if ( pos ? pos.index(cur) > -1 : jQuery(cur).is(selector) ) {
					jQuery.data(cur, "closest", closer);
					return cur;
				}
				cur = cur.parentNode;
				closer++;
			}
		});
	},

	add: function( selector ) {
		var set = typeof selector === "string" ?
				jQuery( selector ) :
				jQuery.makeArray( selector ),
			all = jQuery.merge( this.get(), set );

		return this.pushStack( set[0] && (set[0].setInterval || set[0].nodeType === 9 || (set[0].parentNode && set[0].parentNode.nodeType !== 11)) ?
			jQuery.unique( all ) :
			all );
	},

	eq: function( i ) {
		return i === -1 ?
			this.slice( i ) :
			this.slice( i, +i + 1 );
	},

	first: function() {
		return this.eq( 0 );
	},

	last: function() {
		return this.eq( -1 );
	},

	slice: function() {
		return this.pushStack( Array.prototype.slice.apply( this, arguments ),
			"slice", Array.prototype.slice.call(arguments).join(",") );
	},

	map: function( callback ) {
		return this.pushStack( jQuery.map(this, function(elem, i){
			return callback.call( elem, i, elem );
		}));
	},

	andSelf: function() {
		return this.add( this.prevObject );
	},

	end: function() {
		return this.prevObject || jQuery(null);
	}
});

jQuery.each({
	parent: function(elem){return elem.parentNode;},
	parents: function(elem){return jQuery.dir(elem,"parentNode");},
	next: function(elem){return jQuery.nth(elem,2,"nextSibling");},
	prev: function(elem){return jQuery.nth(elem,2,"previousSibling");},
	nextAll: function(elem){return jQuery.dir(elem,"nextSibling");},
	prevAll: function(elem){return jQuery.dir(elem,"previousSibling");},
	siblings: function(elem){return jQuery.sibling(elem.parentNode.firstChild,elem);},
	children: function(elem){return jQuery.sibling(elem.firstChild);},
	contents: function(elem){return jQuery.nodeName(elem,"iframe")?elem.contentDocument||elem.contentWindow.document:jQuery.makeArray(elem.childNodes);}
}, function(name, fn){
	jQuery.fn[ name ] = function( selector ) {
		var ret = jQuery.map( this, fn );

		if ( selector && typeof selector === "string" ) {
			ret = jQuery.multiFilter( selector, ret );
		}

		ret = this.length > 1 ? jQuery.unique( ret ) : ret;

		if ( name === "parents" && this.length > 1 ) {
			ret = ret.reverse();
		}

		return this.pushStack( ret, name, selector );
	};
});