JS Cookie操作

//写cookies
function setCookie(name, value) {
                var Days = 30;
                var exp = new Date();
                exp.setTime(exp.getTime() + Days * 24 * 60 * 60 * 1000);
                document.cookie = name + "=" + escape(value) + ";expires=" + exp.toGMTString();
            }
//读取cookie
function getCookie(cookie_name) {
        var allcookies = document.cookie;
        //索引长度，开始索引的位置
        var cookie_pos = allcookies.indexOf(cookie_name);

        // 如果找到了索引，就代表cookie存在,否则不存在
        if (cookie_pos != -1) {
            // 把cookie_pos放在值的开始，只要给值加1即可
            //计算取cookie值得开始索引，加的1为“=”
            cookie_pos = cookie_pos + cookie_name.length + 1; 
            //计算取cookie值得结束索引
            var cookie_end = allcookies.indexOf(";", cookie_pos);
            
            if (cookie_end == -1) {
                cookie_end = allcookies.length;

            }
            //得到想要的cookie的值
            var value = unescape(allcookies.substring(cookie_pos, cookie_end)); 
        }
        return value;
    }

            //删除cookies 
            function delCookie(name) {
                var exp = new Date();
                exp.setTime(exp.getTime() - 1);
                var cval = getCookie(name);
                if (cval != null) document.cookie = name + "=" + cval + ";expires=" + exp.toGMTString();
            }