如何使用原生 js 处理 cookie

卓越网的代码，参考学习。

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());
}

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 "";
}

function deleteCookie(cookie_name) {
    var cookie_date = new Date(); // current date & time
    cookie_date.setTime(cookie_date.getTime() - 1);
    document.cookie = cookie_name += "=; expires=" + cookie_date.toGMTString();
}

function checkCookieEnabled(nodeId) {
    setCookie('amznTest', '1', null);
    if (getCookie('amznTest')) {
        deleteCookie('amznTest');
    } else {
        document.getElementById(nodeId).style.display = 'block';
    }
}
checkCookieEnabled('message_warning');