前端如何将数据存储到Cookie里

前端JavaScript可以使用`document.cookie` API 来操作Cookie。以下是设置、读取和删除Cookie的基本步骤：

1. **设置Cookie** (Set Cookie):

   function setCookie(name, value, days) {
     var expires = '';
     if (days) {
       var date = new Date();
       date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
       expires = '; expires=' + date.toUTCString();
     }
     document.cookie = name + '=' + encodeURIComponent(value) + expires + '; path=/';
   }
   // 示例：设置一个名为"username"，值为"JohnDoe"，有效期1天的Cookie
   setCookie('username', 'JohnDoe', 1);

2. **读取Cookie** (Get Cookie):

   function getCookie(name) {
     var cookies = document.cookie.split(';');
     for (var i = 0; i < cookies.length; i++) {
       var cookiePair = cookies[i].trim();
       if (cookiePair.indexOf(name + '=') === 0) {
         return decodeURIComponent(cookiePair.slice(name.length + 1));
       }
     }
     return null;
   }
   // 示例：获取名为"username"的Cookie值
   var username = getCookie('username');

3. **删除Cookie** (Delete Cookie):

   function deleteCookie(name) {
     document.cookie = name + "=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/";
   }
   // 示例：删除名为"username"的Cookie
   deleteCookie('username');