textarea字数限制提示

<script type="text/javascript">  
        //多行文本输入框剩余字数计算  
        function checkMaxInput(obj, maxLen) {  
            if (obj == null || obj == undefined || obj == "") {  
                return;  
            }  
            if (maxLen == null || maxLen == undefined || maxLen == "") {  
                maxLen = 100;  
            }  
  
            var strResult;  
            var $obj = $(obj);  
            var newid = $obj.attr("id") + \'msg\';  
  
            if (obj.value.length > maxLen) { //如果输入的字数超过了限制  
                obj.value = obj.value.substring(0, maxLen); //就去掉多余的字  
                strResult = \'<span id="\' + newid + \'" class=\\'Max_msg\\' ><br/>剩(\' + (maxLen - obj.value.length) + \')字</span>\'; //计算并显示剩余字数  
            }  
            else {  
                strResult = \'<span id="\' + newid + \'" class=\\'Max_msg\\' ><br/>剩(\' + (maxLen - obj.value.length) + \')字</span>\'; //计算并显示剩余字数  
            }  
  
            var $msg = $("#" + newid);  
            if ($msg.length == 0) {  
                $obj.after(strResult);  
            }  
            else {  
                $msg.html(strResult);  
            }  
        }  
  
        //清空剩除字数提醒信息  
        function resetMaxmsg() {  
            $("span.Max_msg").remove();  
        }  
</script>  



调用方法

<textarea id="BZ" name="BZ" style="height: 34px; width: 450px" onkeydown="checkMaxInput(this,80)"  
            onkeyup="checkMaxInput(this,80)" onfocus="checkMaxInput(this,80)" onblur="checkMaxInput(this,80);resetMaxmsg()">  
    </textarea>