JS获取当前日期、当前月第一天、当前月最后一天、当前周前一周、前一个月，前n个月

js获取当前时间YYYY-MM-DD HH:MM:SS

getNowTime: function () {
  let yy = new Date().getFullYear()
  let mm = new Date().getMonth() + 1
  let dd = new Date().getDate()
  let hh = new Date().getHours()
  let mf = new Date().getMinutes() < 10 ? '0' + new Date().getMinutes():new Date().getMinutes()
  let ss = new Date().getSeconds() < 10 ? '0' + new Date().getSeconds():new Date().getSeconds()
  let dateTime = yy + '-' + mm + '-' + dd + ' ' + hh + ':' + mf + ':' + ss
  return dateTime
},

获取当前月第一天

getOneDay(){
 let date=new Date();
 //获取第一天
 date.setDate(1);
 let y=date.getFullYear();
 let m=date.getMonth()+1;
 let d=date.getDate();
 m=m<10?"0"+m:m;
 d=d<10?"0"+d:d;
 let monthOneDay = y+"-"+m+"-"+d+` `+`00:00:00`
 return monthOneDay
},

获取当前月最后一天

getLastDay(){
  //获取最后一天
  let date = new Date();
  let currentMonth = date.getMonth();
  let nextMonth = ++currentMonth;
  let nextMonthFirstDay = new Date(date.getFullYear(), nextMonth, 1);
  let oneDay = 1000 * 60 * 60 * 24;
  let lastTime = new Date(nextMonthFirstDay - oneDay);
  let month = parseInt(lastTime.getMonth() + 1);
  let day = lastTime.getDate();
  if (month < 10) {
 	 month = '0' + month
  }
  if (day < 10) {
  	day = '0' + day
  }
  let monthLastDay = date.getFullYear() + '-' + month + '-' + day+` `+`23:59:59`;
  return monthLastDay;
},

获取当前周前一周的周一周末

var today=new Date();//获取当前时间
var weekday=today.getDay();//获取今天星期几
var lastSunday=new Date(today.getTime() - 1000*60*60*24*(weekday) ); //上周末时间戳
var lastMonday=new Date(today.getTime() - 1000*60*60*24*(weekday+6) ); //上周一时间戳
//最后再进行格式化就好啦

获取前一个月时间

new Date().setMonth(new Date().getMonth() - 1) //获取前一个月时间戳
new Date().setMonth(new Date().getMonth() - n) //获取前n个月时间戳