JavaScript 中两个日期之间的月差 [英] Difference in Months between two dates in JavaScript

问题描述

如何计算 JavaScript 中两个 Date() 对象的差异，同时只返回差异的月数?

How would I work out the difference for two Date() objects in JavaScript, while only return the number of months in the difference?

任何帮助都会很棒:)

推荐答案

相差月数"的定义有很多解释.:-)

The definition of "the number of months in the difference" is subject to a lot of interpretation. :-)

您可以从 JavaScript 日期对象中获取年、月和日.根据您要查找的信息，您可以使用这些信息来计算两个时间点之间有多少个月.

You can get the year, month, and day of month from a JavaScript date object. Depending on what information you're looking for, you can use those to figure out how many months are between two points in time.

例如，即兴的:

function monthDiff(d1, d2) {
    var months;
    months = (d2.getFullYear() - d1.getFullYear()) * 12;
    months -= d1.getMonth();
    months += d2.getMonth();
    return months <= 0 ? 0 : months;
}

function monthDiff(d1, d2) {
    var months;
    months = (d2.getFullYear() - d1.getFullYear()) * 12;
    months -= d1.getMonth();
    months += d2.getMonth();
    return months <= 0 ? 0 : months;
}

function test(d1, d2) {
    var diff = monthDiff(d1, d2);
    console.log(
        d1.toISOString().substring(0, 10),
        "to",
        d2.toISOString().substring(0, 10),
        ":",
        diff
    );
}

test(
    new Date(2008, 10, 4), // November 4th, 2008
    new Date(2010, 2, 12)  // March 12th, 2010
);
// Result: 16

test(
    new Date(2010, 0, 1),  // January 1st, 2010
    new Date(2010, 2, 12)  // March 12th, 2010
);
// Result: 2

test(
    new Date(2010, 1, 1),  // February 1st, 2010
    new Date(2010, 2, 12)  // March 12th, 2010
);
// Result: 1

(请注意 JavaScript 中的月份值以 0 = 一月开始.)

(Note that month values in JavaScript start with 0 = January.)

在上面包括小数月份要复杂得多，因为典型的二月份的三天比八月份的三天(〜9.677％)占该月的更多部分(~10.714％)，当然即使是二月份也是一个移动的目标取决于它是否是闰年.

Including fractional months in the above is much more complicated, because three days in a typical February is a larger fraction of that month (~10.714%) than three days in August (~9.677%), and of course even February is a moving target depending on whether it's a leap year.

还有一些 日期和时间库可用于 JavaScript，这可能会使此类事情变得更容易.

There are also some date and time libraries available for JavaScript that probably make this sort of thing easier.

注意:上面曾经有一个+1，这里:

Note: There used to be a + 1 in the above, here:

months = (d2.getFullYear() - d1.getFullYear()) * 12;
months -= d1.getMonth() + 1;
// −−−−−−−−−−−−−−−−−−−−^^^^
months += d2.getMonth();

那是因为最初我说:

...这会找出两个日期之间有多少个整月，不计算部分月份(例如，不包括每个日期所在的月份).

...this finds out how many full months lie between two dates, not counting partial months (e.g., excluding the month each date is in).

我出于两个原因将其删除:

I've removed it for two reasons:

1. 如果不计算部分月份，结果不是很多(大多数?)人想要的答案，所以我想我应该把它们分开.

1. Not counting partial months turns out not to be what many (most?) people coming to the answer want, so I thought I should separate them out.

即使按照那个定义，它也并不总是有效.:-D (对不起.)

It didn't always work even by that definition. :-D (Sorry.)

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