localStorage二次封装-----设置过期时间

        export default{
            set(key,data,time){
                let obj={
                    data=data,
                    ctime:(new Date()).getTime(),//时间戳，同Date.now()
                    express:1000*60*60//设置过期时间一个小时
                }
                localStorage.setItem(key,JSON.stringify(obj));
            },
            get(key){
                let obj=JSON.parse(localStorage.getItem(key));
                let getItem=(new Date()).getTime();
                if(getItem-obj.ctime>=express){
                    localStorage.removeItem(key);
                    return null;
                }else{
                    return obj.data;
                }
            }
        }