jquery 判断文本框剩余字数

<script type="text/javascript">
$(function(){
	$("#content").bind({
		 "keyup": function (e) {
			 $("#cl").empty();
			 $("#cl").append(smartLen($(this).val()));
			 checkWords($(this).val());
		 }
	});
});
var urlReg ={
	"urlRegText":"((news|telnet|nttp|file|http|ftp|https)://){1}(([-A-Za-z0-9]+(\\.[-A-Za-z0-9]+)*(\\.[-A-Za-z]{2,5}))|([0-9]{1,3}(\\.[0-9]{1,3}){3}))(:[0-9]*)?(/[-A-Za-z0-9_\\$\\.\\+\\!\\*\\(\\),;:@&=\\?/~\\#\\%]*)*"
};
// 字符串长度
function smartLen(str) {
	str = str.replace(/(^[\s\n]+)|([\s\n]+$)/,"").replace(/[\s\n]+/g," ");
    str = str.replace(new RegExp(urlReg.urlRegText, "gi"), new Array(12).join("aa"));
    return Math.ceil(($.trim(str.replace(/[^\u0000-\u00ff]/g, "aa")).length) / 2);
}
function checkWords(content){
	var len = 140-smartLen(content);
	  if (len < 0) {
        $('#txtLen').html('超出&nbsp;<em style="color:#E56C0A">' + (-len) + '</em>&nbsp;字');
		$("#subbtn").attr("disabled",true);
    } else {
        $('#txtLen').html('还能输入&nbsp;<em>' + len + '</em>&nbsp;字');   
	$("#subbtn").attr("disabled",false);		
    }
}
</script> 
 

    <div class="bgcenter">
	    	<div class="t">
		  
		      <div class="r fr" id="txtLen">还能输入&nbsp;<em>140</em>&nbsp;字</div>
		      <div id="cl"></div>
	    	</div>
		
		    <div class="subform" >
		      <form action='http://share.v.t.qq.com/index.php?c=share&a=submit' method="post" target="_self" id="subform">
		      <textarea style="width: 524px;" id="content" name="content"></textarea>	 
		      </form>
		    <input type="button" id="subbtn" value="分享"  title="转播 (快捷键 Ctrl+Enter))"/>
		    </div>	
    </div>