JS中文长度校验

function   changeAlert()
{
var   sms_content=document.all.org_id.value;
var   len   =   sms_content.length;
var   n=0;
for(var   i=0;i <len;i++){
       // alert(sms_content.charCodeAt(i));
                if(sms_content.charCodeAt(i)   <   0   ||   sms_content.charCodeAt(i)   > 255   )
                        {
                           //alert(i+ ", "+sms_content.charCodeAt(i)+ ", "+sms_content.charCodeAt(i));
//alert( "ppp ");
                                n=n+2;
                        } else{
                        n=n+1;
                        }
        }
        if(n>10){
        alert(n+"=输入过长！");
        }else{
        alert("OK");
        }
}