本地存储 ： 特别重要
sessionStorage
localStorage
*****区别
- sessionStorage关闭页面就消失
- localStorage 除非手动清空，否则就算关闭页面也不会清空
*****区别
*******本地存储进去的value类型都是字符串
增加：
sessionStorage|localStorage.setItem(key,value)
sessionStorage|localStorage.key = value;
sessionStorage|localStorage['key'] = value;
获取：
sessionStorage|localStorage.getItem(key)
sessionStorage|localStorage.key
sessionStorage|localStorage['key']
删除：
全部删除 : sessionStorage|localStorage.clear();
指定删除 : sessionStorage|localStorage.removeItem(key);