在JavaScript中将日期添加到日期 [英] Adding months to a Date in JavaScript

问题描述

可能重复：

Javascript函数将X个月添加到日期

我想在用户输入结束日期添加2个月。如何在结束日期添加2个月并显示？

I'd like to add 2 months to a user-input end date. How can I add 2 months to the end date and display it?

/**
* Click "Cal" on end date
*/
function getEndDate() {
if(!document.getElementById('startdate').value.length) {
    alert("Start date must be set first.");
}
else {
    prevEndDate = document.getElementById('enddate').value;
    displayCalendar(document.forms[0].enddate,'yyyy/mm/dd',
        document.getElementById('enddatebutton'));
}
}

/**
* Click "Cal" on expiry date
*/
function getExpiryDate() {
if(!document.getElementById('enddate').value.length) {
    alert("End date must be set first.");
}
else {
    prevExpiryDate = document.getElementById('expirydate').value;
    displayCalendar(document.forms[0].expirydate,'yyyy/mm/dd',
        document.getElementById('expirydatebutton'));
 }
}

任何帮助表示赞赏。谢谢！

Any help is appreciated. Thanks!

推荐答案

您需要获得添加月份的业务规则。简单的解决方案是：

You need to get business rules for adding months. The simple solution is:

function addMonths(dateObj, num) {
  return dateObj.setMonth(dateObj.getMonth() + num);
}

然而，这将改变7月31日至9月31日，将转换为10月1日。此外，1月31日加1个月是2月31日，根据是否是闰年，将转换为3月2日或3日。

However, that will change 31 July to 31 September, which will be converted to 1 October. Also, 31 January plus 1 month is 31 February which will be converted to 2 or 3 March depending on whether it's a leap year or not.

您可能会期望第一个9月30日，第二个是2月28日或29日（取决于是否是闰年）。

You might expect the first to be 30 September and the second to be 28 or 29 February (depending on whether it's a leap year or not).

因此，如果你想要结束月份的话，你需要做类似的事情：

So if you want "end of months" be observed, you need to do something like:

function addMonths(dateObj, num) {

    var currentMonth = dateObj.getMonth() + dateObj.getFullYear() * 12;
    dateObj.setMonth(dateObj.getMonth() + num);
    var diff = dateObj.getMonth() + dateObj.getFullYear() * 12 - currentMonth;

    // If don't get the right number, set date to 
    // last day of previous month
    if (diff != num) {
        dateObj.setDate(0);
    } 
    return dateObj;
} 

但请与负责业务规则的人核实这是他们想要的。

But check with whoever is responsible for the business rules that that is what they want.

以上情况很好，但是为了回应McShaman的评论，这里有一个更简单的版本检查月份翻转：

The above works well, but in response to McShaman's comment here is a version with a simpler check for the month roll–over:

function addMonths(date, months) {
  var d = date.getDate();
  date.setMonth(date.getMonth() + +months);
  if (date.getDate() != d) {
    date.setDate(0);
  }
  return date;
}

// Add 12 months to 29 Feb 2016 -> 28 Feb 2017
console.log(addMonths(new Date(2016,1,29),12).toString());

// Subtract 1 month from 1 Jan 2017 -> 1 Dec 2016
console.log(addMonths(new Date(2017,0,1),-1).toString());

// Subtract 2 months from 31 Jan 2017 -> 30 Nov 2016
console.log(addMonths(new Date(2017,0,31),-2).toString());

// Add 2 months to 31 Dec 2016 -> 28 Feb 2017
console.log(addMonths(new Date(2016,11,31),2).toString());

这篇关于在JavaScript中将日期添加到日期的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！