问题描述
当我有一个月的二月时，如何让下面的代码工作?目前它正在进入这一天，然后在进入 if 之前停止以确定它是否是闰年.
How can I get the code below to work when I have a month of february? Currently it is getting to the day and then stopping before getting to the if to determine whether it is a leap year.
if (month == 2) {
if (day == 29) {
if (year % 4 != 0 || year % 100 == 0 && year % 400 != 0) {
field.focus();
field.value = month +'/' + '';
}
}
else if (day > 28) {
field.focus();
field.value = month +'/' + '';
}
}
推荐答案
使用日期对象 用于日期时间的东西，例如
It's safer to use Date objects for datetime stuff, e.g.
isLeap = new Date(year, 1, 29).getMonth() == 1
由于人们一直在问这到底是如何工作的，这与 JS 如何从年-月-日计算日期值有关(详细信息 此处).基本上，它首先计算当月的第一天，然后添加 N -1 天.因此，当我们要求非闰年的 2 月 29 日时，结果将是 2 月 1 日 + 28 天 = 3 月 1 日:
Since people keep asking about how exactly this works, it has to do with how JS calculates the date value from year-month-day (details here). Basically, it first calculates the first of the month and then adds N -1 days to it. So when we're asking for the 29th Feb on a non-leap year, the result will be the 1st Feb + 28 days = 1st March:
> new Date(2015, 1, 29)
< Sun Mar 01 2015 00:00:00 GMT+0100 (CET)
在闰年，1 日 + 28 = 2 月 29 日:
On a leap year, the 1st + 28 = 29th Feb:
> new Date(2016, 1, 29)
< Mon Feb 29 2016 00:00:00 GMT+0100 (CET)
在上面的代码中，我将日期设置为 2 月 29 日，然后查看是否发生了翻转.如果不是(月份仍为1，即二月)，则这是闰年，否则为非闰年.
In the code above, I set the date to 29th Feb and look if a roll-over took place. If not (the month is still 1, i.e. February), this is a leap year, otherwise a non-leap one.
这篇关于javascript 查找闰年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！