function addCookie(objName,objValue,objHours){//添加cookie
   var str = objName + "=" + escape(objValue);
   if(objHours > 0){//为0时不设定过期时间，浏览器关闭时cookie自动消失
    var date = new Date();
    var ms = objHours*3600*1000;
    date.setTime(date.getTime() + ms);
    str += "; expires=" + date.toGMTString();
   }
   document.cookie = str;
  }
  
  function getCookieTop(objName){//获取指定名称的cookie的值
   var arrStr = document.cookie.split("; ");
   for(var i = 0;i < arrStr.length;i ++){
    var temp = arrStr[i].split("=");
    if(temp[0] == objName) return unescape(temp[1]);
   } 
  }
  
  function delCookie(name){//为了删除指定名称的cookie，可以将其过期时间设定为一个过去的时间
   var date = new Date();
   date.setTime(date.getTime() - 10000);
   document.cookie = name + "=a; expires=" + date.toGMTString();
  }
  
  function allCookie(){//读取所有保存的cookie字符串
   var str = document.cookie;
   if(str == ""){
    str = "没有保存任何cookie";
   }
 
  }