JavaScript 获取当前、昨天和明天日期的多种实现方式

  function getDay(day){
    var today = new Date()
    // 获取时间戳(毫秒级)
    /*
      day为1，则是，明天的时间戳
      day为-1，则是，昨天的时间戳
      day为-2，则是，前天的时间戳
    */
    var targetday_milliseconds = today.getTime() + 1000 * 60 * 60 * 24 * day
    // Date.setTime(时间戳)：设置当前日期的时间
    today.setTime(targetday_milliseconds)
    console.log('today=', today) // today= Sun Mar 05 2023 16:14:56 GMT+0800 (中国标准时间)
    var tYear = today.getFullYear() // 年
    var tMonth = today.getMonth() // 月
    var tDate = today.getDate() // 日
    tMonth = this.doHandleMonth(tMonth + 1)
    tDate = this.doHandleMonth(tDate)
    console.log('返回年月日=', tYear + '-' + tMonth + '-' + tDate)
    return tYear + '-' + tMonth + '-' + tDate
  }
  function doHandleMonth(month) {
    var m = month
    if (month.toString().length == 1) {
      m = '0' + month
    }
    return m
  }

/* 
  * @params date 日期
  * @params type 日期 prev/current/next 昨天/今天/明天
  * @params fmt 日期拼接符
*/
function getDays(date, type, fmt) {
    let currentDate = new Date(date)
    let y = currentDate.getFullYear()
    let m = currentDate.getMonth() + 1
    let d = currentDate.getDate()
    function dateFormat(date, fmt) {
        let y = new Date(date).getFullYear()
        let m = new Date(date).getMonth() + 1
        let d = new Date(date).getDate()
        return `${y}${fmt}${m}${fmt}${d}`
    }
    switch (type) {
        case "prev":
            if (d - 1 < 1) {
                if (m - 1 < 1) {
                    y = y - 1
                    m = 12
                } else {
                    m = m - 1
                }
                d = new Date(y, m, 0).getDate()
            } else {
                d = d - 1
            }
            break
        case "current":
            break
        case "next":
            if (d + 1 > new Date(y, m, 0).getDate()) {
                if (m + 1 > 12) {
                    y = y + 1
                    m = 1
                    d = 1
                } else {
                    m = m + 1
                    d = 1
                }
            } else {
                d = d + 1
            }
            break;
    default:
      break;
    }
    return dateFormat(new Date(`${y}-${m}-${d}`), fmt)
}
console.log(getDays(new Date('2023-5-13'), "prev", "-"));
console.log(getDays(new Date('2023-5-30'), "next", "-"));
console.log(getDays(new Date('2023-5-31'), "next", "-"));

//昨天的时间
 var day1 = new Date();
 day1.setTime(day1.getTime()-24*60*60*1000);
 var s1 = day1.getFullYear()+"-" + (day1.getMonth()+1) + "-" + day1.getDate();
 //今天的时间
 var day2 = new Date();
 day2.setTime(day2.getTime());
 var s2 = day2.getFullYear()+"-" + (day2.getMonth()+1) + "-" + day2.getDate();
 //明天的时间
 var day3 = new Date();
 day3.setTime(day3.getTime()+24*60*60*1000);
 var s3 = day3.getFullYear()+"-" + (day3.getMonth()+1) + "-" + day3.getDate();
 //拼接时间
 function show(){
  var str = "" + s1 + "至" + s2;
  return str;
 }
 //赋值doubleDate
 $('#dateS').val(show());

function writeCurrentDate() {
   var now = new Date();
   var year = now.getFullYear(); //得到年份
   var month = now.getMonth();//得到月份
   var date = now.getDate();//得到日期
   var day = now.getDay();//得到周几
   var hour = now.getHours();//得到小时
   var minu = now.getMinutes();//得到分钟
   var sec = now.getSeconds();//得到秒
 　　  var MS = now.getMilliseconds();//获取毫秒
   var week;
   month = month + 1;
   if (month < 10) month = "0" + month;
   if (date < 10) date = "0" + date;
   if (hour < 10) hour = "0" + hour;
   if (minu < 10) minu = "0" + minu;
   if (sec < 10) sec = "0" + sec;
   if （MS < 100）MS = "0" + MS;
   var arr_week = new Array("星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六");
   week = arr_week[day];
   var time = "";
   time = year + "年" + month + "月" + date + "日" + " " + hour + ":" + minu + ":" + sec + " " + week;
   //当前日期赋值给当前日期输入框中（jQuery easyUI）
   $("#currentDate").html(time);
   //设置得到当前日期的函数的执行间隔时间，每1000毫秒刷新一次。
   var timer = setTimeout("writeCurrentDate()", 1000);
  }

 //昨天的时间 
 var day1 = new Date();
 day1.setDate(day1.getDate() - 1);
 var s1 = day1.format("yyyy-MM-dd");
 //前天的时间
 var day2 = new Date();
 day2.setDate(day2.getDate() - 2);
 var s2 = day2.format("yyyy-MM-dd");

/**
 *对Date的扩展，将 Date 转化为指定格式的String
 *月(M)、日(d)、小时(h)、分(m)、秒(s)、季度(q) 可以用 1-2 个占位符，
 *年(y)可以用 1-4 个占位符，毫秒(S)只能用 1 个占位符(是 1-3 位的数字)
 *例子：
 *(new Date()).Format("yyyy-MM-dd hh:mm:ss.S") ==> 2006-07-02 08:09:04.423
 *(new Date()).Format("yyyy-M-d h:m:s.S")  ==> 2006-7-2 8:9:4.18
 */
 Date.prototype.format = function (fmt) {
  var o = {
   "M+": this.getMonth() + 1, //月份
   "d+": this.getDate(), //日
   "h+": this.getHours(), //小时
   "m+": this.getMinutes(), //分
   "s+": this.getSeconds(), //秒
   "q+": Math.floor((this.getMonth() + 3) / 3), //季度
   "S": this.getMilliseconds() //毫秒
  };
  if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
  for (var k in o)
   if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
  return fmt;
 }

var d = new Date();
d.setHours(d.getHours(), d.getMinutes() - d.getTimezoneOffset());
console.log(d.toISOString())