A CoffeeScript version of my lightweight character counter for jQuery.

jquery.counter.js.coffee

(($) ->
  
  # Author: Mohamad El-Husseini, www.mohamad.im
  # Light weight character counter for jQuery.
  # Example: http://jsfiddle.net/yHPg7/6/
  "use strict"
  $.fn.counter = (options) ->
    defaultText = ->
      options.defaultText.replace /minSize/g, options.minSize
    count = (elem) ->
      size = elem.val().length
      target = elem.siblings(options.targetClass)
      if size is 0
        target.html defaultText()
      else if size < options.minSize
        target.html (options.minSize - size) + options.minWarning
      else if size >= options.minSize and size < options.warningSize
        target.html "&nbsp;"
      else if size >= options.warningSize and 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
    options = $.extend($.fn.counter.defaults, options)
    @each ->
      elem = $(this)
      count elem
      elem.keyup ->
        count elem

      elem.closest("form").submit ->
        if elem.val().length < options.minSize
          $(this).find(options.targetClass).fadeOut("fast").fadeIn("fast").fadeOut("fast").fadeIn "fast"
          false

      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