JavaScript中的日期操作

Question

I have this string for example "November 8, 2016 - December 7, 2016" which I want to extract the two dates in the this format: YYYY-MM-DD . Now, I managed to get the dates in the format I want in the following way:

HTML:

<span id="selecDate">November 8, 2016 - December 7, 2016</span>

Javascript:

date = $('#selecDate').text().split('-');
begin = new Date(date[1]);
begin = begin.toISOString().split('T')[0];

The problem is that date = ["November 8, 2016 ", " December 7, 2016"]

and begin = "Wed Dec 07 2016 00:00:00 GMT+0200 (IST)"

when in second line but in the last line the value of begin changes to "2016-12-06" , one day earlier. Any idea how can I avoid it?

I'm working from (GMT+02:00) time zone

Answer 1

When you execute toISOString() the date you get back is in UTC time so it takes the time back 2 hours (because of your current timezone). Midnight on Dec 06 in IST is 22:00 in UTC time the day before.

If you wish to keep your timestamps in local time, you can use a .toLocaleDateString() , toLocaleString() or even just .toString() on your date object:

begin = new Date('December 7, 2016').toLocaleDateString();

Note that the date format is slightly different:

a.toLocaleDateString() "12/7/2016"

a.toLocaleString() "12/7/2016, 12:00:00 AM"

a.toString() "Wed Dec 07 2016 00:00:00 GMT+0200 (IST)"

Answer 2

As MDN says in, method toISOString() :

The timezone is always zero UTC offset.

And when you create your new Date('December 7, 2016') , what you get is:

Wed Dec 07 2016 00:00:00 GMT+0200

So in UTC, the hours are subtracted by 2, giving you the day before.

Solution :

begin = begin.getFullYear() + '-' + (begin.getMonth() + 1) + '-' + begin.getDate();

will result in: "2016-12-07".

Answer 3

date = ["November 8, 2016 ", " December 7, 2016"];
var b = new Date(date[1]);

//use these get methods to avoid all the confusion
var begin = b.getFullYear()+"-"+(b.getMonth()+1)+"-"+b.getDate();
console.log(_begin);

Answer 4

You should not parse strings with the Date constructor, especially when they are a format other than that specified in ECMA-262 as the behaviour is implementation dependent.

If you need Date objects, you should either use a library (eg moment.js , fecha.js ) and provide the format to parse or write a simple function to parse the format to a date (see below).

However, if you just want a string in a different format, just reformat the string and avoid Dates altogether:

 // Reformat a date string in format MMMM d, yyyy to yyyy-mm-dd function reformatDate(s) { var b = s.match(/\\w+/g) || []; var months = {jan:'01',feb:'02',mar:'03',apr:'04',may:'05',jun:'06', jul:'07',aug:'08',sep:'09',oct:'10',nov:'11',dec:'12'}; return b.length == 3? b[2] + '-' + months[b[0].toLowerCase().substr(0,3)] + '-' + ('0' + b[1]).slice(-2) : ''; } console.log(reformatDate('November 8, 2016')) 

The following functions parse a date in MMMM d, yyyy format to a Date object, then format it in yyyy-mm-dd format:

 // Parse date string in format MMMM d, yyyy eg November 8, 2016 function parseDate(s) { var months = 'jan feb mar apr may jun jul aug sep oct nov dec'.split(' '); var b = s.match(/\\w+/g) || []; var m = months.indexOf(b[0].toLowerCase().substr(0,3)); var d = new Date(b[2], m, b[1]); return d && d.getMonth() == m? d : new Date(NaN); } function toISODate(d) { function z(n){return (n<10?'0':'')+n} return d.getFullYear() + '-' + z(d.getMonth()+1) + '-' + z(d.getDate()); } console.log(toISODate(parseDate('November 8, 2016'))) 

Using a library like moment.js you'd do:

 'November 8, 2016 - December 7, 2016'.split(' - ').forEach(function(s) { var d = moment(s,'MMMM D, YYYY').format('YYYY-MM-DD'); console.log(d); }); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.17.1/moment.js"></script>