Ограничение и подсчёт символов

Подсчитывает количество введённых символов в текстовое поле, и не позволяет ввести более заданного количества. Также отображает количество введённых символов.

<form action="" name="limitForm">
   <span class="form"><input type="text" name="limit" value="" /></span>
</form>

<script type="text/javascript">
   var ns6=document.getElementById&&!document.all

   function restrictinput(maxlength, e, placeholder)
      {
      if (window.event && event.srcElement.value.length >= maxlength)
         return false;
      else if (e.target && e.target == eval(placeholder) && e.target.value.length >= maxlength)
         {
         var pressedkey = /[a-zA-Z0-9\.\,\/]/;
         if (pressedkey.test(String.fromCharCode(e.which)))
            e.stopPropagation();
         }
      }

   function countlimit(maxlength, e, placeholder)
      {
      var theform = eval(placeholder);
      var lengthleft = maxlength-theform.value.length;
      var placeholderobj = document.all ? document.all[placeholder] : document.getElementById(placeholder);
      if (window.event || e.target&&e.target == eval(placeholder))
         {
         if (lengthleft < 0)
             theform.value = theform.value.substring(0, maxlength);
         placeholderobj.innerHTML = lengthleft
         }
      }

   function displaylimit(thename, theid, thelimit)
      {
      var theform = theid != "" ? document.getElementById(theid) : thename;
      var limit_text = 'можно ввести <span id="' + theform.toString() + '">' + thelimit + '</span> символов';
      if (document.all || ns6)
         document.write(limit_text)
      if (document.all)
         {
         eval(theform).onkeypress = function(){ return restrictinput(thelimit, event, theform)}
         eval(theform).onkeyup = function(){ countlimit(thelimit, event, theform)}
         }
      else if (ns6)
         {
         document.body.addEventListener('keypress', function(event) { restrictinput(thelimit, event, theform) }, true);
         document.body.addEventListener('keyup', function(event) { countlimit(thelimit, event, theform) }, true);
         }
      }

   displaylimit("document.limitForm.limit", "", 20);
</script>