控制texterea长度，并显示剩余字数，只能在IE上运行

<script>
function checklen(obj){
  var lenE = obj.value.length;
  var lenC = 0;
  var CJK = obj.value.match(/[u4E00-u9FA5uF900-uFA2D]/g);
  if (CJK != null) lenC += CJK.length;
    tno.innerText = obj.maxlength - lenC - lenE ;
    if (tno.innerText < 0) {
      var tmp = 0
      var cut = obj.value.substring(0, obj.maxlength);
      for (var i=0; i<cut.length; i++){
      tmp += /[u4E00-u9FA5uF900-uFA2D]/.test(cut.charAt(i)) ? 2 : 1;
      if (tmp > obj.maxlength) break;
    }
    obj.value = cut.substring(0, i);
  }
}
</script>
<body onload="tno.innerText = s1.maxlength;">
<textarea name="s1" rows="5" cols="50" maxlength="100" onpropertychange="checklen(this)"></textarea>
剩余<span id="tno"></span>个字符

附：Javascript中的trim和replace函数===============
//triml();
triml = function () {
  for (var i = 0; i < this.length; i++) {
    if (this.charcodeat (i) > 32) {
      return this.substr (i, this.length);
    }
  }
  return this;
}
 
//trimr();
trimr = function () {
  for (var i = this.length; i > 0; i--) {
    if (this.charcodeat (i) > 32) {
    return this.substring (0, i + 1);
    }
  }
  return this;
}
 
//trimwhite();
trimwhite = function() {
  this = this.triml ();
  return this.trimr ();
}
 
//replace();
function replace():string {
  var str:string = string(arguments[0]);
  var re_str:string = string(arguments[1]);
  var new_str:string = string(arguments[2]);
  if (arguments.length<3||re_str=="") {
    return str;
  }
  while (str.indexof(re_str) != -1 && str != "") {
    str_b = str.indexof(re_str);
    str_e = str_b+re_str.length-1;
    if (str_b != 0 && str_e != str.length-1) {
      str = str.substr(0, str_b)+new_str+str.substr(str_e+1, str.length-1);
    } else if (str_b == 0) {
      str = new_str+str.substr(str_e+1, str.length-1);
    } else {
      str = str.substr(0, str_b)+new_str;
    }
  }
  return str;
}