detecting two keys pressed down

HTML

<h1>hi</h1>

<textarea cols=80 rows=10></textarea>

JavaScript

(function ($) {
    $(

    function () {

        /* somethign odd seems to be happening. if you hit  cmd+a and hold it both are registered properly.  but if you release a the keyup for a is not registered.  if you release cmd first then a then the keyup for both is registered. only tried it on chrome */
        
        var checkCt = function (e, ct,k) {
            $('textarea').val('on ' + e + ' the count is: ' + ct);
            console.log(e,ct,k,keysDown);
        },
        keyct = 0,
            keysDown = {},
            thisKey, lastKey;

        $('body').on('keydown', function (e) {
            console.log(e.keyCode ,' is going down');
            thisKey = e.keyCode;
            if (!keysDown[thisKey]) {
                keysDown[thisKey] = thisKey;
                keyct++;
                checkCt('down', keyct, e.keyCode);


            }



            lastKey = thisKey;
            return false;
        })
        $('body').on('keyup', function (e) {
            console.log(e.keyCode ,' is going up');
            thisKey = e.keyCode;
            if (keysDown[thisKey]) {
                keysDown[thisKey] = undefined;
                keyct--;
                checkCt('up', keyct,e.keyCode);

            }
        });

    }); // on ready

})(jQuery);