(function($){
 $.fn.count_chars = function(options){

  var defaults = {
   limit: 140,
   counter: "span.counter"
  };
  
  var options = $.extend(defaults, options)
  
  return this.each(function(){
    var e = $(this)
    
    e.keyup(function(){
	    var chars = options.limit - e.val().length
      $(options.counter).html(chars)
      if (options.submit_button) {
	      // submit disable
        $(options.submit_button).attr("disabled", (chars < 0))
      }
    }).keyup()
  })
 }
})(jQuery);