限制textbox或textarea输入字符长度的JS代码

<script language=javascript>
<!--

String.prototype.len=function(){
return this.replace(/[^x00-xff]/g,"**").length;
}

//Set maxlength for multiline TextBox
function setMaxLength(object,length)
{
var result = true;
var controlid = document.selection.createRange().parentElement().id;
var controlValue = document.selection.createRange().text;
if (controlid == object.id && controlValue != "")
{
result = true;
}
else if (object.value.len() >= length)
{
result = false;
}
if (window.event)
{
window.event.returnValue = result;
return result;
}
}

//Check maxlength for multiline TextBox when paste
function limitPaste(object,length)
{
var tempLength = 0;
if(document.selection)
{
if(document.selection.createRange().parentElement().id == object.id)
{
tempLength = document.selection.createRange().text.len();
}
}
var tempValue = window.clipboardData.getData("Text");
tempLength = object.value.len() + tempValue.len() - tempLength;
if (tempLength > length)
{
tempLength -= length;
//alert(tempLength);
//alert(tempValue);
var tt="";
for(var i=0;i<tempValue.len()-tempLength;i++)
{
if(tt.len()<(tempValue.len()-tempLength))
tt=tempValue.substr(0,i+1);
else
break;
}
tempValue=tt;
window.clipboardData.setData("Text", tempValue);
}

window.event.returnValue = true;
}

//-->
</script>