jquery.filter.js

/*
 * Duck Punched Filter
 * May 1, 2010
 * Corey Hart @ http://www.codenothing.com
 */
(function( $, undefined ) {

// Keep a copy of the old filter for reference
var old = $.fn.filter;

// Create space for holding filter custom filter functions
$.filters = {};

// Overload the filter method
$.fn.filter = function( pass, args, fn ) {
	// Make sure the qualifier was passed, otherwise use old filter
	if ( args === undefined ) {
		return old.apply( this, arguments );
	}

	// Reorganize
	if ( $.isArray( pass ) ) {
		fn = args;
		args = pass;
		pass = false;
	}
	else if ( $.isFunction( args ) ) {
		fn = args;
		if ( typeof pass == 'boolean' ) {
			args = [];
		} else {
			args = pass;
			pass = false;
		}
	}

	// Setup qualifier to allow a stored reference or anonymous function
	fn = typeof fn == 'string' ? $.filters[ fn ] : fn;
	var self = this, elems = [], i = -1, l = self.length;

	// Allow for full control of elems stack creation
	if ( pass === true ) {
		// Convert the current stack into array of elements, and spot
		// it at the first position
		args.unshift( self.toArray() );
		elems = fn.apply( self, args ) || [];
	}
	else {
		// Configure new set of elements based on qualifier and the 2 first 
		// spots in the arguments for index and current element
		args.unshift( null );
		args.unshift( null );
		for ( ; ++i < l; ) {
			args[ 0 ] = i;
			args[ 1 ] = self[ i ];
			if ( fn.apply( self[ i ], args ) === true ) {
				elems.push( self[ i ] );
			}
		}
	}

	// Make the new jquery object
	return self.pushStack( elems, 'filter', fn );
};

})( jQuery );