JS 判断字符字节长度

//获得字符字节长度
function getStrByteLen(str)
{
     if(str =="") {
         return true;
     } else {
         var out = str.replace(/[^/x00-/xff]/g,"**");
         //alert("out.length = " + out.length);
         if(out.length > 5) {
             alert("输入字符长度过长");
             return false;
         }
         return true;
    }
}