// DISCLAIMER: 
// This is not my code. (got it from : http://www.scriptiny.com/2012/09/jquery-input-textarea-limiter/)
// I just wanted to have a central repo

(function($) {
    $.fn.extend( {
        limiter: function(limit, elem) {
            $(this).on("keyup focus", function() {
                setCount(this, elem);
            });
            function setCount(src, elem) {
                var chars = src.value.length;
                if (chars > limit) {
                    src.value = src.value.substr(0, limit);
                    chars = limit;
                }
                elem.html( limit - chars );
            }
            setCount($(this)[0], elem);
        }
    });
})(jQuery);

//To setup the limiter, simply include a call similar to the one below:
var elem = $("#chars");
$("#text").limiter(100, elem);

http://www.scriptiny.com/2012/09/jquery-input-textarea-limiter/

This little jQuery snippet will let you quickly add a limit counter to input fields to display available remaining characters. A nice feature to include for improved user experience.

Input & Textarea Character Limit Display with jQuery

jQuery