Check if entered date is valid in JavaScript

Question

I have a JSON data containing dates (in mm/dd/yyyy format) which I am converting to Date object using the Date constructor like new Date(year, month, day). I want to return the date object only if the date string is valid. For e.g., for the string '12/08/1992', I should get Tue Dec 08 1992 as expected. But if I pass an invalid date like '15/08/1992' by doing new Date(1992, 14, 8) (month is always n-1 for the Date constructor), I get 'Mon Mar 08 1993', which is not as expected.

Is it possible to check somehow that the entered date is invalid? I can't use any libraries for this.

Yes it is. What have you tried so far? What research have you done? — random_user_name, May 24 '18 at 17:44
_Can't_ and _want_ are entirely different - I don't usually recommend libraries, but when I do, it's momentjs. — chazsolo, May 24 '18 at 18:02

score 0 · Answer 1 · answered May 24 '18 at 17:52

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You can always implement your custom date validator. Keep it simple if you don't want to use any libraries.

answered May 24 '18 at 17:52

VHS

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Nishant Dixit · Answer 2 · 2018-05-24T18:06:22.847

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0?[1-9] => 0...9
|  => optional
1[012] => 10..12 
[\/] => / (MM/DD/YYYY)
[12][0-9] => 10 ..... 29
3[01] => 30...31
d{4} => any with length 4 (0000...9999)

var regex = /^(0?[1-9]|1[012])[\/](0?[1-9]|[12][0-9]|3[01])[\/]\d{4}$/;

console.log(regex.test(`12/08/1992`));

console.log(regex.test(`15/08/1992`));

edited May 24 '18 at 18:06

answered May 24 '18 at 17:57

Nishant Dixit

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This seems to work, but can you explain that regex a bit? – darKnight May 24 '18 at 17:59
@maverick Updated. – Nishant Dixit May 24 '18 at 18:06
Code-only answers are not useful, especially in this case. Break it down. Explain what you did, what it does, why it works. – random_user_name May 24 '18 at 18:08
@NishantDixit: This does not work in all cases. `console.log(regex.test(`11/31/1992`))` gives `true`, even though November has only 30 days. – darKnight May 24 '18 at 18:13
Here I used regex for validate general format of Date, I did not consider above use case in this regex I think this is not possible to handle this use case using regex from my knowledge. – Nishant Dixit May 24 '18 at 18:20
You can manually handle this use case but code will go lengthy – Nishant Dixit May 24 '18 at 18:20

Check if entered date is valid in JavaScript

2 Answers2