function getCookie(cookie_name) {
    var allcookies = document.cookie;
    var cookie_pos = allcookies.indexOf(cookie_name);

    // 如果找到了索引，就代表cookie存在，
    // 反之，就说明不存在。
    if (cookie_pos != -1) {
        // 把cookie_pos放在值的开始，只要给值加1即可。
        cookie_pos += cookie_name.length + 1;
        var cookie_end = allcookies.indexOf(";", cookie_pos);

        if (cookie_end == -1) {
            cookie_end = allcookies.length;
        }

        var value = unescape(allcookies.substring(cookie_pos, cookie_end));
    }

    return value;
}

/**
 *
 * @access public
 * @return void
 **/
function setCookie(cookie_name, cookie_value) {
    var expiration = new Date((new Date()).getTime() + 86400000);   // 86400 - 24 hours
    document.cookie = cookie_name + "=" + escape(cookie_value)+ "; expires ="
+ expiration.toGMTString() + "; path=" + "/" + "; _domain=" + window.location.hostname + "; ";
}