Javascript 从 Date 对象中减去天/月/年
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Subtracting days/months/years from a Date object
提问by dave
var inputDate = '20/4/2010'.split('/');
var dateFormatted = new Date(parseInt(inputDate[2]), parseInt(inputDate[1]), parseInt(inputDate[0]));
var expiryDate = (dateFormatted.getDate() - 1) + '/' + dateFormatted.getMonth() + '/' + (dateFormatted.getFullYear() + year);
This is the Javascript code I'm using to work out an expiry date given a user inputted date. Currently, the expiry date is original date minus one day and original year minus X.
这是我用来计算给定用户输入日期的到期日期的 Javascript 代码。目前，到期日是original date minus one day and original year minus X。
The problems with this code, firstly, it doesn't take into account invalid dates. For example, if the user supplied date is '1/10/2010', the expiry date will be '0/10/2013' (assuming the expiry date is +3 years).
这段代码的问题，首先是它没有考虑无效日期。例如，如果用户提供的日期为“1/10/2010”，则到期日期将为“0/10/2013”（假设到期日期为 +3 年）。
I could do something like:
我可以做这样的事情：
var inputDate = '20/4/2010'.split('/');
var day = parseInt(inputDate[0]);
var month = parseInt(inputDate[1]);
var year = parseInt(inputDate[2]);
if (day < 1)
{
if (month == ...)
{
day = 31
month = month - 1;
}
else
{
day = 30
month = month - 1;
}
}
var dateFormatted = new Date(parseInt(inputDate[2]), parseInt(inputDate[1]), parseInt(inputDate[0]));
var expiryDate = (dateFormatted.getDate() - 1) + '/' + dateFormatted.getMonth() + '/' + (dateFormatted.getFullYear() + year);
But more problems arise... Firstly, the code gets a little convoluted. Secondly, this check would have to be done on the day. and then the month. Is there a cleaner, simpler way?
但更多的问题出现了......首先，代码变得有点复杂。其次，这项检查必须在当天进行。然后是月份。有没有更干净、更简单的方法？
Also, there's a certain circumstance that would involve me needing to calculate the expiry date to the 'end of the month' for that date. For example:
此外，在某些情况下，我需要将到期日期计算为该日期的“月底”。例如：
Expiry date is: +3 years
User date is: '14/10/2010'
Expiry date is: '31/10/2013'
I was hoping the Date objectwould support these calculations but according to https://developer.mozilla.org/en/JavaScript/Reference/global_objects/date, it seems not...
我希望Date object能支持这些计算，但根据https://developer.mozilla.org/en/JavaScript/Reference/global_objects/date，它似乎不是......
回答by Noah
Easy way to see if a date inputed is a valid date:
查看输入的日期是否为有效日期的简单方法：
var d = Date.parse('4/20/2010');
if (isNaN(d.valueOf())) {
alert ("bad date value");
}
Then, here is a dateAdd function that I use regularly. Extends the Date object, so it's easy to use:
然后，这是我经常使用的 dateAdd 函数。扩展了 Date 对象，所以它很容易使用：
Date.prototype.dateAdd = function(size,value) {
value = parseInt(value);
var incr = 0;
switch (size) {
case 'day':
incr = value * 24;
this.dateAdd('hour',incr);
break;
case 'hour':
incr = value * 60;
this.dateAdd('minute',incr);
break;
case 'week':
incr = value * 7;
this.dateAdd('day',incr);
break;
case 'minute':
incr = value * 60;
this.dateAdd('second',incr);
break;
case 'second':
incr = value * 1000;
this.dateAdd('millisecond',incr);
break;
case 'month':
value = value + this.getUTCMonth();
if (value/12>0) {
this.dateAdd('year',value/12);
value = value % 12;
}
this.setUTCMonth(value);
break;
case 'millisecond':
this.setTime(this.getTime() + value);
break;
case 'year':
this.setFullYear(this.getUTCFullYear()+value);
break;
default:
throw new Error('Invalid date increment passed');
break;
}
}
Then just use:
然后只需使用：
var d = new Date();
d.dateAdd('day', -1).dateAdd('year', 3);
T'da
达达
回答by Gunjit
A similar question has been answered here:
这里已经回答了一个类似的问题：
How to add/subtract dates with javascript?
Similar thing can be done for months and years.
类似的事情可以持续数月甚至数年。
For e.g.
例如
var date = new Date('2011','01','02');
alert('the original date is '+date);
var newdate = new Date(date);
newdate.setMonth(newdate.getMonth() - 7);
var nd = new Date(newdate);
alert('the new date is '+nd);
回答by DoXicK
var currentDate = new Date(year,month,day);
var expiryDate = new Date();
expiryDate.setTime(currentDate.getTime() + (3 * 365 * 24 * 60 * 60 * 1000));
using the number of seconds past 1970 is fine for this :-) oh, you have more rules. well after that you will still have to check for those cases...
使用 1970 年以后的秒数很好：-) 哦，你有更多的规则。在那之后，您仍然需要检查这些情况......
回答by Dr.Molle
Maybe this will be useful to you: http://code.google.com/p/datejs/wiki/APIDocumentation
也许这对你有用：http: //code.google.com/p/datejs/wiki/APIDocumentation
