Bikin jQuery textarea autogrow, tolong dikoreksi dulu hehehe

Bikin jQuery textarea autogrow, tolong dikoreksi dulu hehehe.

$(document).ready(function() {
    function cektkp_growtextarea(textarea) {
        textarea.each(function() {
            textarea = $(this);
            textarea.css('overflow', 'hidden');
            var pos = textarea.position();
            var growerid = 'textarea_grower_' + textarea.attr('id');
            textarea.after('<div style="position:absolute;z-index:-1000;visibility:hidden;top:' + pos.top + ';height:' + textarea.height() + '" id="' + growerid + '"></div>');
            var growerdiv = $('#' + growerid);
            growerdiv.css({
                'font-size': textarea.css('font-size'),
                'width': textarea.width()
            });
            growerdiv.html(textarea.val().replace(/\n/g, "<br />."));
            if (textarea.val() == '') {
                growerdiv.html('.');
            }
            textarea.height(growerdiv.height());
            textarea.keyup(function() {
                growerdiv.html($(this).val().replace(/\n/g, "<br />."));
                if ($(this).val() == '') {
                    growerdiv.html('.');
                }
                $(this).animate({
                    height: growerdiv.height()
                }, 70);
            });
        });
    }
    cektkp_growtextarea($('textarea.autogrow'));
});

demo:

http://cektkp.com/demo/index.php?page=textarea_autogrow