CODEWITHSUNDEEP
javascript
Theraloss
Theraloss

Reputation: 700

Javascript: setDate(DATE + day) not update month

I created this function to increment a date (for a 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:

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?

Upvotes: 3

Views: 25888

Answers (4)

acdcjunior
acdcjunior

Reputation: 135862

I think I see what's the trouble.

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?

Some points you must consider:

  • The creation of the date new Date(2013, 7, 3) does not create the date 03/Jul/2013:
    • Months are zero-based, meaning they go from 0 to 11, not 1 to 12.
      • This way, the month 7 actually is August.

  • The statement moreDay.setDate(act.getDate()+1) does not make moreDay the date act plus one day. Because:
    • date.getDate() returns the day of the month of the date variable
    • date.setDate(int) sets the day of date (just the day, leaving the year and month intact)
    • What the statement moreDay.setDate(act.getDate()+1) does then is:
      • Set moreDay's day the value of act's day plus one.

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

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.

Upvotes: 14

PHP Worm...
PHP Worm...

Reputation: 4224

One way to do this:

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

Upvotes: 0

MaxArt
MaxArt

Reputation: 22637

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:

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 Date object January is 0, hence the - 1.

This alternative should be faster than setDate:

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

Or you could define your Date object directly with an added day:

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

Upvotes: 7

tckmn
tckmn

Reputation: 59363

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

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

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

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);
}

Upvotes: 5

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