向 Javascript 日期对象添加天数，并增加月份
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Add days to Javascript Date object, and also increment month
提问by NimChimpsky
Looking over the previous questions and answersit appeared this should work :
查看以前的问题和答案，似乎这应该有效：
var palindrome = new Date('2011-11-11');
var december = new Date('2011-11-11');
december.setDate(palindrome.getDate()+20);
//should be december, but in fact loops back over to Nov 1st)
my jsFiddle
我的jsFiddle
is there a simple way to ensure that months are incremented correctly, or have I missed something obvious ?
是否有一种简单的方法可以确保月份正确递增，或者我是否遗漏了一些明显的内容？
回答by nogola
You could do it like this:
你可以这样做：
var dayOffset = 20;
var millisecondOffset = dayOffset * 24 * 60 * 60 * 1000;
december.setTime(december.getTime() + millisecondOffset);
回答by tvanfosson
The getMonth()call returns a value between 0 and 11, where 0 is January and 11 is December, so 10 means November. You need to increment the value by 1 when using it in a string. If you simply output it as a string you'll see that it has the correct date. Note I also had to change the starting date format. It didn't seem to like 2011-11-11so I made it 11/11/2011. http://jsfiddle.net/9HLSW/
该getMonth()调用返回0到11，其中0是一月和11月之间的值，所以10种月手段。在字符串中使用时，需要将该值加 1。如果您只是将其作为字符串输出，您将看到它具有正确的日期。注意我还必须更改开始日期格式。它似乎不喜欢2011-11-11所以我做到了11/11/2011。 http://jsfiddle.net/9HLSW/
回答by Samuel Liew
Your code is correct, however you are converting it to a string wrongly.
您的代码是正确的，但是您错误地将其转换为字符串。
getMonth()starts with 0as January, and ends with 11as December. So all you need to do is add 1 to the month like this:
getMonth()从0开始作为一月，以11结束作为十二月。所以你需要做的就是像这样给月份加 1：
alert(endDate.getFullYear() + "-" + (endDate.getMonth()+1) +"-"+ endDate.getDate());
Notice the additional brackets- cos you are performing a math operation while concatenating strings. You won't want to end up with "101" as the month.
请注意附加括号- 因为您在连接字符串时正在执行数学运算。您不会希望以“ 101”作为月份结束。
To see whether you got the date correct, use endDate.toDateString()to display the date in a fully qualified name (i.e.: January - December).
要查看日期是否正确，请使用endDate.toDateString()以完全限定名称显示日期（即：一月 - 十二月）。
alert(endDate.toDateString());
For more info on the Date object, check out this sectionin w3schools
有关 Date 对象的更多信息，请查看w3schools 中的此部分
