我正试图形成一个日期,这是3个月前的当前日期。我通过下面的代码得到当前月份

var currentDate = new Date();
var currentMonth = currentDate.getMonth()+1;

你能给我提供一个逻辑来计算和形成一个日期(date数据类型的对象),考虑到当月份是一月(1)时,日期前3个月将是十月(10)吗?


当前回答

d.setMonth在浏览器try中修改了本地时间

 const calcDate = (m) => {
    let date = new Date();
    let day = date.getDate();
    let month = date.getMonth() + 1;
    let year = date.getFullYear();
    let days = 0;

    if (m > 0) {
      for (let i = 1; i < m; i++) {
        month += 1;
        if (month > 12) {
          year += 1;
          month = 1;
        }
        days += new Date(year, month, 0).getDate();
      }
    } else {
      for (let i = m; i < 0; i++) {
        month -= 1;
        if (month < 1) {
          year -= 1;
          month = 12;
        }
        days -= new Date(year, month, 0).getDate();
      }
    }

    const newTime = date.getTime() + 3600 * 24 * 1000 * days;
    return new Date(newTime);
  };

calcDate(3)//+3 month

其他回答

var todayDate =新日期。slice (0) (10); var d =新日期(todayDate); d . setMonth (d . getMonth () - 3); 游戏机。log (todayDate) log (d . toISOString(游戏机)。slice (0) (10));

var d = new日期("2013/01/01"); console.log (d.toLocaleDateString ()); d.setMonth(d.getMonth() + 18); console.log (d.toLocaleDateString ());

Following code give me Just Previous Month From Current Month even the date is 31/30 of current date and last month is 30/29/28 days:

   <!DOCTYPE html>
<html>
<body>

<p>Click the button to display the date after changing the month.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {

var d = new Date("March 29, 2017"); // Please Try the result also for "March 31, 2017" Or "March 30, 2017"
var OneMonthBefore =new Date(d);

OneMonthBefore.setMonth(d.getMonth(),0);
if(OneMonthBefore.getDate() < d.getDate()  )
{
d.setMonth(d.getMonth(),0);
}else
{
d.setMonth(d.getMonth()-1);

}

    document.getElementById("demo").innerHTML = d;
}
</script>

</body>
</html>

我建议使用一个名为Moment.js的库。

它经过了良好的测试,可以跨浏览器和服务器端工作(我在Angular和Node项目中都使用它)。它对区域日期有很好的支持。

http://momentjs.com/

var threeMonthsAgo = moment().subtract(3, 'months');

console.log(threeMonthsAgo.format()); // 2015-10-13T09:37:35+02:00

.format()返回ISO 8601格式的日期字符串表示形式。你也可以像这样使用自定义日期格式:format('dddd, MMMM Do YYYY, h:mm:ss a')

传递一个JS Date对象和一个你想加/减多少个月的整数。monthsToAdd可以是正的也可以是负的。返回一个JS日期对象。

如果您的originalDateObject是3月31日,并且您传递-1作为monthsToAdd,那么您的输出日期将是2月28日。

如果您经过了大量的月份,比如36个月,它也会正确地处理年份调整。

const addMonthsToDate = (originalDateObject, monthsToAdd) => {
  const originalDay = originalDateObject.getUTCDate();
  const originalMonth = originalDateObject.getUTCMonth();
  const originalYear = originalDateObject.getUTCFullYear();

  const monthDayCountMap = {
    "0": 31,
    "1": 28,
    "2": 31,
    "3": 30,
    "4": 31,
    "5": 30,
    "6": 31,
    "7": 31,
    "8": 30,
    "9": 31,
    "10": 30,
    "11": 31
  };

  let newMonth;
  if (newMonth > -1) {
    newMonth = (((originalMonth + monthsToAdd) % 12)).toString();
  } else {
    const delta = (monthsToAdd * -1) % 12;
    newMonth = originalMonth - delta < 0 ? (12+originalMonth) - delta : originalMonth - delta;
  }

  let newDay;

  if (originalDay > monthDayCountMap[newMonth]) {
    newDay = monthDayCountMap[newMonth].toString();
  } else {
    newDay = originalDay.toString();
  }

  newMonth = (+newMonth + 1).toString();

  if (newMonth.length === 1) {
    newMonth = '0' + newMonth;
  }

  if (newDay.length === 1) {
    newDay = '0' + newDay;
  }

  if (monthsToAdd <= 0) {
    monthsToAdd -= 11;
  }

  let newYear = (~~((originalMonth + monthsToAdd) / 12)) + originalYear;

  let newTime = originalDateObject.toISOString().slice(10, 24);

  const newDateISOString = `${newYear}-${newMonth}-${newDay}${newTime}`;

  return new Date(newDateISOString);
};