(function ($) {
    $.fn.autogrow = function () {
        this.filter('textarea').each(function () {
            var $this = $(this),
                minHeight = $this.height(),
                shadow = $('<div></div>').css({
                    position:   'absolute',
                    top: -10000,
                    left: -10000,
                    width: $(this).width(),
                    fontSize: $this.css('fontSize'),
                    fontFamily: $this.css('fontFamily'),
                    lineHeight: $this.css('lineHeight'),
                    resize: 'none'
                }).addClass('shadow').appendTo(document.body),
                update = function () {
                    var t = this;
                    setTimeout(function () {
                        var val = t.value.replace(/</g, '&lt;')
                                .replace(/>/g, '&gt;')
                                .replace(/&/g, '&amp;')
                                .replace(/\n/g, '<br/>&nbsp;');
    
                        if ($.trim(val) === '') {
                            val = 'a';
                        }
    
                        shadow.html(val);
                        $(t).css('height', Math.max(shadow[0].offsetHeight + 20, minHeight));
                    }, 0);
                };

            $this.change(update).keyup(update).keydown(update).focus(update);
            update.apply(this);
        });

        return this;
    };

}(jQuery));