//navigator.cookieEnabled 检测浏览器是否支持cookie


//获得一个正确格式的过期时间
function getExpDate(days, hours, minutes)
{
    var expDate = new Date();
    if(typeof(days) == "number" && typeof(hours) == "number" && typeof(hours) == "number")
    {
        expDate.setDate(expDate.getDate() + parseInt(days));
        expDate.setHours(expDate.getHours() + parseInt(hours));
        expDate.setMinutes(expDate.getMinutes() + parseInt(minutes));
        return expDate.toGMTString();
    }
}

function getCookieVal(offset)
{
    var endstr = document.cookie.indexOf(";", offset);
    if(endstr == -1)
    {
        endstr = document.cookie.length;
    }
    res = document.cookie.substring(offset, endstr);
    if(getCookieVal.arguments.length==2)
    {
        ary = res.split('&');
        res = '';
        for(var i=0; i<ary.length; i++)
        {
            temp = ary[i].split('=');
            if(temp[0].toLowerCase()==getCookie.arguments[1].toLowerCase())
                res = temp[1];
        }
    }
    return unescape(res);
}

//读取cookie中保存的值，参数name为cookie项的名称。如果该cookie项不存在则返回一个空字符串。
function getCookie(name)
{
    var arg = name + "=";
    var alen = arg.length;
    var clen = document.cookie.length;
    var i = 0;
    while(i < clen)
    {
        var j = i + alen;
        if (document.cookie.substring(i, j) == arg)
        {
            if(getCookie.arguments.length==2)
            {
                return getCookieVal(j,getCookie.arguments[1]);
            }
            else
                return getCookieVal(j);
        }
        i = document.cookie.indexOf(" ", i) + 1;
        if(i == 0) break;
    }
    return '';
}

//保存cookie项的值，其中第一、二两个参数分别为cookie项的名称和值。如果想为其设置一个过期时间，那么就需要设置第三个参数，这里需要通过getExpDate()获得一个正确格式的参数。
function setCookie(name, value, expires, path, domain, secure)
{   
    if(value=='') value='null';
    document.cookie = name + "=" + escape(value) +
        ((expires) ? "; expires=" + expires : "") +
        ((path) ? "; path=" + path : "") +
        ((domain) ? "; domain=" + domain : "") +
        ((secure) ? "; secure" : "");        
}

//删除一个已存在的cookie项，实际上是通过让该项过期。
function deleteCookie(name,path,domain) 
{
    if(getCookie(name))
    {
        document.cookie = name + "=" +
            ((path) ? "; path=" + path : "") +
            ((domain) ? "; domain=" + domain : "") +
            "; expires=Thu, 01-Jan-70 00:00:01 GMT";
    }
}