Javascript：setDate(DATE + day) 不更新月份

Javascript: setDate(DATE + day) not update month

提问by Theraloss

I created this function to increment a date (for a jQuery UI Datepicker):

我创建了这个函数来增加一个日期（对于 jQuery UI Datepicker）：

function addDay(date) {
    var moreDay = new Date();
    var decomposed = date.split("-");
    var act = new Date(decomposed[2], decomposed[1], decomposed[0]);
    moreDay.setDate(act.getDate()+1);
    return moreDay;
}

So, it scomposes the date (ex: 12-06-2013 (dd-mm-YYYY)) and put the values into a new Date, after that it addes a day. It works, but the month not change. Example, I changed the function into this:

因此，它组合日期（例如：12-06-2013 (dd-mm-YYYY)）并将这些值放入一个新的日期中，然后添加一天。它有效，但月份不变。例如，我将函数更改为：

function addDay() {
    var moreDay = new Date();
    var act = new Date(2013, 7, 3);
    moreDay.setDate(act.getDate()+1);
    alert(moreDay);
}

And it returns Jun 4th 2013.. How it's possible?

它返回 2013 年 6 月 4 日.. 怎么可能？

回答by acdcjunior

I think I see what's the trouble.

我想我明白有什么问题了。

function addDay() {
    var moreDay = new Date();
    var act = new Date(2013, 7, 3);
    moreDay.setDate(act.getDate()+1);
    alert(moreDay);
}

And it returns Jun 4th 2013.. How it's possible?

它返回 2013 年 6 月 4 日.. 怎么可能？

Some points you must consider:

您必须考虑的一些要点：

• The creation of the date new Date(2013, 7, 3)does notcreate the date 03/Jul/2013:
  • Months are zero-based, meaning they go from 0 to 11, not 1 to 12.
    • This way, the month 7actually is August.
      
      
• The statement moreDay.setDate(act.getDate()+1)does not makemoreDaythe date actplus one day. Because:
  • date.getDate()returns the dayof the monthof the datevariable
  • date.setDate(int)sets the dayof date(justthe day, leaving the year and month intact)
  • What the statement moreDay.setDate(act.getDate()+1)does then is:
    • Set moreDay's daythe value of act's day plus one.

• 日期的创作new Date(2013, 7, 3)并没有创建之日起03 /七月/ 2013：
  • 月份是从零开始的，这意味着它们从 0 到 11，而不是从 1 到 12。
    • 这样，月份7实际上是八月。
      
      
• 声明moreDay.setDate(act.getDate()+1)没有使moreDay日期act加一天。因为：
  • date.getDate()返回日当月的的date变量
  • date.setDate(int)设置一天的date（仅仅一天，留下的年份和月份完好）
  • 该语句的 moreDay.setDate(act.getDate()+1)作用是：
    • 设置moreDay's day's day的值act加一。

In other words, as moreDay's value is new Date()(which is the current day - right now 11/Jun/2013where I live), and act's day is 3, the statement evaluationthen really is:

换句话说， asmoreDay的值是new Date()（即当前日期 - 现在是我居住的11/Jun/2013），而act's day is 3，那么语句评估实际上是：

Step #1: moreDay.setDate( act.getDate() + 1 );
Step #2: moreDay.setDate( (03/Aug/2013).getDate() + 1 );
Step #3: moreDay.setDate( 03 + 1 );
Step #4: moreDay.setDate( 4 );
Step #5: (11/Jun/2013).setDate( 4 );
Step #6: (04/Jun/2013)

Thus ending Jun 4th 2013.

从而于 2013 年 6 月 4 日结束。

回答by Doorknob

moreDay.setDate(act.getDate()+1);

This will only add one day. Why do you expect it to add a month, too?

这只会增加一天。为什么你期望它也增加一个月？

If you want to add a month also, try this:

如果你还想增加一个月，试试这个：

function addDay() {
    var moreDay = new Date();
    var act = new Date(2013, 7, 3);
    moreDay.setMonth(act.getMonth()+1); // add one month
    moreDay.setDate(act.getDate()+1); // add one day
    alert(moreDay);
}

回答by MaxArt

It's not clear what you want to do with your function. If you want to take a date and add a day, try with this:

不清楚你想用你的函数做什么。如果您想约会并添加一天，请尝试以下操作：

function addDay(date) {
    var decomposed = date.split("-"),
        moreDay = new Date(decomposed[2], decomposed[1] - 1, decomposed[0]);
    moreDay.setDate(moreDay.getDate() + 1);
    alert(moreDay);
}

Please take note that in common dd-mm-yyyy dates, January is 1, whereas to define a Dateobject January is 0, hence the - 1.

请注意，在常见的 dd-mm-yyyy 日期中，一月是 1，而定义Date对象一月是 0，因此- 1.

This alternative should be faster than setDate:

这种替代方法应该比setDate：

moreDay.setTime(moreDay.getTime() + 864e5);

Or you could define your Dateobject directly with an added day:

或者您可以Date直接添加一天来定义您的对象：

moreDay = new Date(decomposed[2], decomposed[1] - 1, +decomposed[0] + 1);

回答by PHP Worm...

One way to do this:

一种方法：

var now = new Date();
        function addDays(date,days) {
            var currentDate = date.getDate();
            date.setDate(currentDate + days);
            alert(date);
        }
    addDays(now,14)