以前做项目时候经常用到多行输入框字数的控制以及统计显示的情况，综合了几种情况后现在固定用了这个脚本。
例如 要输入描述textbox
<div>
<h3>
描述：</h3>
<asp:TextBox runat="server" ID="tbdesciption" Height="200px" TextMode="MultiLine" onkeyup="textCounter(this,'shengyu',500)" onkeydown="textCounter(this,'shengyu',500)"
AutoCompleteType="None" Columns="100" MaxLength="1000" Width="500px"></asp:TextBox>
</div>
<div>您还可以输入:<input type="text" readonly="readonly" style=" width:22px; color:Red; border:0px;" mce_style=" width:22px; color:Red; border:0px;" id="shengyu" />个字</div>
javascript代码：
function textCounter(fieldId, countfieId, maxlimit) {
var fieldEle = fieldId;
var countfieldEle = document.getElementById(countfieId);
if (fieldEle == null || countfieldEle == null) {
return false;
}
if (fieldEle.value.gblen() > maxlimit) // too long... trim it
//fieldEle.value = fieldEle.value.substring(0, maxlimit);
fieldEle.value = fieldEle.value.gbtrim(maxlimit, '');
else
countfieldEle.value = maxlimit - fieldEle.value.gblen();
}
String.prototype.gblen = function() {
var len = 0;
for (var i = 0; i < this.length; i++) {
if (this.charCodeAt(i) > 127 || this.charCodeAt(i) == 94) {
len += 1;
}
else {
len++;
}
}
return len;
}
String.prototype.gbtrim = function(len, s) {
var str = '';
var sp = s || '';
var len2 = 0;
for (var i = 0; i < this.length; i++) {
if (this.charCodeAt(i) > 127 || this.charCodeAt(i) == 94) {
len2 += 1;
}
else {
len2++;
}
}
if (len2 <= len) {
return this;
}
len2 = 0;
len = (len > sp.length) ? len - sp.length : len;
for (var i = 0; i < th
