粗劣的时间计算当天、昨天、上月、本月、本年

在别人获取上月的基础上获取

import moment from 'moment'
function getPreMonth(date) {
  date = moment(date).format('YYYY-MM-DD');
  var arr = date.split('-');
  var year = arr[0]; //获取当前日期的年份
  var month = arr[1]; //获取当前日期的月份
  var day = arr[2]; //获取当前日期的日
  var days = new Date(year, month, 0);
  days = days.getDate(); //获取当前日期中月的天数
  var year2 = year;
  var month2 = parseInt(month) - 1;
  if (month2 == 0) { //如果是1月份，则取上一年的12月份
    year2 = parseInt(year2) - 1;
    month2 = 12;
  }
  var day2 = day;
  var days2 = new Date(year2, month2, 0);
  days2 = days2.getDate();
  if (day2 > days2) { //如果原来日期大于上一月的日期，则取当月的最大日期。比如3月的30日，在2月中没有30
    day2 = days2;
  }
  if (month2 < 10) {
    month2 = '0' + month2; //月份填补成2位。
  }
  var t2 = year2 + '-' + month2 + '-' + 1;
  return new Date(t2);
}


export function selDate(e){
  let dateArr = [];
  var now = new Date() // 当前日期
  var nowYear = now.getFullYear() //当前年
  var nowMonth = now.getMonth() //当前月 （值为0~11）
  var d = now.getDate() //当天
  // 0 当天 1 昨天 2上月 3本月 4本年
  switch(e){
    case '0':dateArr = [new Date(nowYear, nowMonth, d), new Date(nowYear, nowMonth, d)];break;
    case '1':dateArr = [new Date(new Date(nowYear, nowMonth, d).getTime() - 86400000), new Date(new Date(nowYear, nowMonth, d).getTime() - 86400000)];break;
    case '2':dateArr = [getPreMonth(new Date(nowYear, nowMonth, d)) , new Date(getPreMonth(new Date(nowYear, nowMonth, d)).getFullYear(),nowMonth, 0)];break;
    case '3':dateArr = [new Date(nowYear, nowMonth, 1), new Date(nowYear, nowMonth, new Date(nowYear, nowMonth+1, 0).getDate())];break;
    case '4':dateArr = [new Date(nowYear, 0, 1), new Date(nowYear, nowMonth,d)];break;
  }
  return dateArr
}