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;
    //alert("添加cookie成功");
   }
  
   function getCookie(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";
    }
    alert(str);
   }