dayjs 获取本周、上一周、下一周的第一天和最后一天的日期（周一&周日）

npm i dayjs --save

import dayjs from 'dayjs';

/**
* 获取日期的函数
*/   
updateWeek(weekOffset) {
      const today = dayjs()
      const timestamp = Math.round(new Date())
      const date = new Date(timestamp)
      const weekday = date.getDay()
      const targetWeek = weekday === 0 ? weekOffset - 1 : weekOffset
      this.beginDate = today.add(targetWeek, 'week').startOf('week').add(1, 'day').format('YYYY-MM-DD')
      this.endDate = today.add(targetWeek, 'week').endOf('week').add(1, 'day').format('YYYY-MM-DD')
    }

/**
* 获取本周
*/  
this.updateWeek(0)

/**
* 获取上周
*/  
this.updateWeek(-1)

/**
* 获取下周
*/  
this.updateWeek(1)