(function($){

    // jQuery autoGrowInput plugin by James Padolsey
    // See related thread: http://stackoverflow.com/questions/931207/is-there-a-jquery-autogrow-plugin-for-text-fields

        $.fn.autoGrowInput = function(o) {

            o = $.extend({
                maxWidth: 1000,
                minWidth: 0,
                comfortZone: 35 //How much space should be in input after text
            }, o);

            this.filter('input:text').each(function(){

                var minWidth = o.minWidth || $(this).width(),
                    val = '',
                    input = $(this),
                    testSubject = $('<tester/>').css({
                        position: 'absolute',
                        top: -9999,
                        left: -9999,
                        width: 'auto',
                        fontSize: input.css('fontSize'),
                        fontFamily: input.css('fontFamily'),
                        fontWeight: input.css('fontWeight'),
                        letterSpacing: input.css('letterSpacing'),
                        whiteSpace: 'nowrap'
                    }),
                    check = function() {

                        if (val === (val = input.val())) {return;}

                        // Enter new content into testSubject
                        var escaped = val.replace(/&/g, '&amp;').replace(/\s/g,'&nbsp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
                        testSubject.html(escaped);

                        // Calculate new width + whether to change
                        var testerWidth = testSubject.width(),
                            newWidth = (testerWidth + o.comfortZone) >= minWidth ? testerWidth + o.comfortZone : minWidth,
                            currentWidth = input.width(),
                            isValidWidthChange = (newWidth < currentWidth && newWidth >= minWidth)
                                                 || (newWidth > minWidth && newWidth < o.maxWidth);

                        // Animate width
                        if (isValidWidthChange) {
                            input.width(newWidth);
                        }

                    };

                testSubject.insertAfter(input);

                $(this).bind('keyup keydown blur update focus', check);

            });

            return this;

        };

    })(jQuery);

$('input').autoGrowInput();