moment.js 常用（几天前、相差几天、自然周、自然月）
let pickDate = moment(this.searchForm.date);
let firstDay = pickDate.day(0).format('YYYYMMDD');//上周天
let lastDay = pickDate.day(7).format('YYYYMMDD');//周天
let previousDate = moment(this.searchForm.date).subtract(1, "weeks").format("YYYY-MM-DD");//上周