javascript 如何在javascript中获得“约会前一天”？
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How to get "the day before a date" in javascript?
提问by Arbiter
These two stack overflow questions ask a similar question, but their solution doesn't seem to work for me: Javascript YesterdayJavascript code for showing yesterday's date and todays date
这两个堆栈溢出问题提出了一个类似的问题，但他们的解决方案似乎对我不起作用： Javascript Yesterday Javascript code for shows today's date and todays date
Given a date, I need the date of the prior day (the day before). Here's a fiddle with the solution suggested above, and a scenario that doesn't work for me: http://jsfiddle.net/s3dHV/
给定一个日期，我需要前一天（前一天）的日期。这是上面建议的解决方案的小提琴，以及对我不起作用的场景：http: //jsfiddle.net/s3dHV/
var date = new Date('04/28/2013 00:00:00');
var yesterday = new Date();
yesterday.setDate(date.getDate() - 1);
alert('If today is ' + date + ' then yesterday is ' + yesterday);
For me, that alerts
对我来说，这提醒
If today is Sun Apr 28 2013 00:00:00 GMT-0400 (Eastern Daylight Time) then yesterday is Monday May 27 2013 11:12:06 GMT-0400 (Eastern Daylight Time).
如果今天是 2013 年 4 月 28 日星期日 00:00:00 GMT-0400（东部夏令时间），那么昨天是 2013 年 5 月 27 日星期一 11:12:06 GMT-0400（东部夏令时间）。
Which is obviously incorrect. Why?
这显然是不正确的。为什么？
回答by Pointy
You're making a whole new date.
你在进行一个全新的约会。
var yesterday = new Date(date.getTime());
yesterday.setDate(date.getDate() - 1);
That'll make you a copyof the first date. When you call setDate(), it just affects the day-of-the-month, not the whole thing. If you start with a copy of the original date, and then set the day of the month back, you'll get the right answer.
那会让你复制第一次约会。当您调用 时setDate()，它只会影响月份中的某一天，而不是整个事情。如果您从原始日期的副本开始，然后将月份中的日期重新设置，您将得到正确的答案。
回答by Vadim
Try this:
试试这个：
var date = new Date('04/28/2013 00:00:00');
var yesterday = new Date(date.getTime() - 24*60*60*1000);
回答by Riyanto Wibowo
var allmonths = [
'01', '02', '03', '04', '05', '06', '07', '08', '09', '10', '11', '12'
];
var alldates = [
'01', '02', '03', '04', '05', '06', '07', '08', '09', '10',
'11', '12', '13', '14', '15', '16', '17', '18', '19', '20',
'21', '22', '23', '24', '25', '26', '27', '28', '29', '30', '31'
];
var today = "2014-12-25";
var aDayBefore = new Date(today);
aDayBefore.setDate(aDayBefore.getDate() - 1);
document.write(aDayBefore.getFullYear()
+ '-' + allmonths[aDayBefore.getMonth()]
+ '-' + alldates[aDayBefore.getDate() - 1]);
