cookie形式">完整的cookie形式：

document.cookie = “user=xxx;expires=失效时间;path=访问路径;domain=访问域名;secure=安全https通信”

//保存cookie，并显示.
document.cookie = "user=" + encodeURIComponent("粒");
alert(decodeURIComponent(document.cookie));

保存cookie时候有个会话过期时间.如果没有设置，会在浏览器关闭的时候自动清理cookie.

    //设置过期时间，过期cookie自动删除
    var date = new Date();
    date.setDate(date.getDate()+7);
    document.cookie = "user=" + encodeURIComponent("粒")+";expires="+date;
    alert(decodeURIComponent(document.cookie));

    //删除cookie
    document.cookie = "user=" + encodeURIComponent("粒")+";expires="+new Date(0);

//设置cookie
function setCookie(name, value, expires, path, domain, secure) {
    var cookieName = encodeURIComponent(name) + '=' + encodeURIComponent(value);
    if (expires instanceof Date) {
        cookieName += '; expires=' + expires;
    }
    if (path) {
        cookieName += '; path=' + path;
    }
    if (domain) {
        cookieName += '; domain=' + domain;
    }
    if (secure) {
        cookieName += '; secure';
    }
    document.cookie = cookieName;
}

//获取Cookie
function getCookie(name) {
    var cookieName = encodeURIComponent(name) + '=';
    var cookieStart = document.cookie.indexOf(cookieName);
    var cookieValue = null;

    if (cookieStart > -1) {
        var cookieEnd = document.cookie.indexOf(';', cookieStart);
        if (cookieEnd == -1) {
            cookieEnd = document.cookie.length;
        }
        cookieValue = decodeURIComponent(document.cookie.substring(cookieStart + cookieName.length, cookieEnd));
    }
    return cookieValue;
}

alert(getCookie('email'));



//过期时间
function setCookieDate(day) {           //传递一个天数，比如传递7，就7天后失效
    var date = null;
    if (typeof day == 'number' && day > 0) {
        date = new Date();
        date.setDate(date.getDate() + day);
    } else {
        throw new Error('您传递的天数不合法！必须是数字且大于0');
    }
    return date;
}