js 读写cookie实现代码

//读写cookie函数
function getcookie(c_name)
{
 if (document.cookie.length > 0)
 {
  c_start = document.cookie.indexof(c_name + "=")
  if (c_start != -1)
  {
   c_start = c_start + c_name.length + 1;
   c_end   = document.cookie.indexof(";",c_start);
   if (c_end == -1)
   {
    c_end = document.cookie.length;
   }
   return unescape(document.cookie.substring(c_start,c_end));
  }
 }
 return null
}

function setcookie(c_name,value,expiredays)
{
 var exdate = new date();
 exdate.setdate(exdate.getdate() + expiredays);
 document.cookie = c_name + "=" +escape(value) + ((expiredays == null) ? "" : ";expires=" + exdate.togmtstring()); //使设置的有效时间正确。增加togmtstring()
}