js怎么设置cookie的值

document.cookie = "键=值; expires=过期时间; path=路径; domain=域名; secure; samesite";

function setCookie(name, value, days) {
    let expires = "";
    if (days) {
        const date = new Date();
        date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
        expires = "; expires=" + date.toUTCString();
    }
    document.cookie = name + "=" + (value || "") + expires + "; path=/; samesite=Lax";
}

// 使用示例
setCookie("username", "JohnDoe", 7); // 设置一个名为username的cookie，值为JohnDoe，过期时间为7天

function getCookie(name) {
    const nameEQ = name + "=";
    const ca = document.cookie.split(';');
    for (let i = 0; i < ca.length; i++) {
        let c = ca[i];
        while (c.charAt(0) === ' ') c = c.substring(1, c.length);
        if (c.indexOf(nameEQ) === 0) return c.substring(nameEQ.length, c.length);
    }
    return null;
}

// 使用示例
console.log(getCookie("username")); // 输出: JohnDoe

function eraseCookie(name) {
    document.cookie = name + '=; Max-Age=-99999999; path=/; samesite=Lax';
}

// 使用示例
eraseCookie("username"); // 删除名为username的cookie