Lightweight jQuery character counter plugin.

jquery.counter.js

(function ($) {
    // Author: Mohamad El-Husseini, www.mohamad.im
    // Light weight character counter for jQuery.
    // Example: http://jsfiddle.net/yHPg7/6/

    "use strict";

    $.fn.counter = function (options) {
        options = $.extend($.fn.counter.defaults, options);

        function defaultText() {
            return options.defaultText.replace(/minSize/ig, options.minSize);
        }

        function count(elem) {
            var size = elem.val().length, target = elem.siblings(options.targetClass);
            if (size === 0) {
                target.html(defaultText());
            } else if (size < options.minSize) {
                target.html((options.minSize - size) + options.minWarning);
            } else if (size >= options.minSize && size < options.warningSize) {
                target.html('&nbsp;');
            } else if (size >= options.warningSize && size < options.maxSize) {
                target.html((options.maxSize - size) + options.maxWarning);
            } else if (size >= options.maxSize) {
                elem.val(elem.val().substring(0, options.maxSize));
                target.html("0" + options.maxWarning);
            }
        }

        this.each(function () {
            var elem = $(this);
            count(elem);
            elem.keyup(function () {
                count(elem);
            });
            elem.closest('form').submit(function () {
                if (elem.val().length < options.minSize) {
                    $(this).find(options.targetClass).fadeOut('fast').fadeIn('fast').fadeOut('fast').fadeIn('fast');
                    return false;
                }
            });
            return elem;
        });
    };

    $.fn.counter.defaults = {
        minSize: 15,
        minWarning: " more to go...",
        maxSize: 25,
        maxWarning: " characters remaining...",
        warningSize: 20,
        targetClass: '.help-block',
        defaultText: 'Enter at least minSize characters.'
    };
})(jQuery);