// 设置cookie   
function setCookie(c_name, value, expiredays) {
    var exdate = new Date();
    exdate.setDate(exdate.getDate() + expiredays);
    document.cookie = c_name + "=" + escape(value) + ";expires = " + exdate.toGMTString() + ";path = /";
}

// 读取cookie   
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 ""
}

// 清除cookie 
function clearCookie(name) {
    setCookie(name, "", -1);
}