Dollars amount real-time update

dollars.js

(function ($) {
    var DOLLARS = 20;

    $.fn.dollars = function () {
        $(this).each(function () {
            var $table = $(this);

            $table.find('tr:first-child th:not(:first-child)').each(function (index) {
                var $label = $('<span/>').appendTo($(this)),
                    $fields = $table.find('td:nth-child(' + (index + 2) + ') input');

                $fields.on('input', function () {
                    var used = Array.prototype.reduce.call($fields, function (sum, el) {
                        return sum + (parseInt(el.value, 10) || 0);
                    }, 0);

                    if (used > DOLLARS) {
                        $label.text(' ($' + (used - DOLLARS) + ' overused)')
                            .addClass('text-danger');
                    } else {
                        $label.text(' ($' + (DOLLARS - used) + ' left)')
                            .removeClass('text-danger');
                    }
                });

                $fields.eq(0).trigger('input');
            });
        });
    }
})(jQuery);

jQuery(function ($) {
    $('table').dollars();
});