Dayjs: Validation .isValid() doesn't work always

[dakshshah96]

The .isValid() validation doesn't function correctly under the following condition:

• When the the day part is 31 for a month which didn't have 31 days.

Some instances where .isValid() returns true for a date that is invalid:

• dayjs().isValid('1995-02-31')
• dayjs().isValid('1995-03-31')
• dayjs().isValid('1995-04-31')
• dayjs().isValid('1995-06-31')
• dayjs().isValid('1995-09-31')
• dayjs().isValid('1995-11-31')

[mixrich]

@dakshshah96
.isValid() method has't arguments and passed value is discarded like if you call dayjs().isValid(). And you know, that dayjs() return current date which is always valid

[mixrich]

Moreover, isValid doesn't validate if passed date is exists, it's just validate that date was parsed correctly. So, if you pass dayjs('2018-11-41').isValid() the date will be parsed as 2018-12-10 and isValid will return true anyway

[prantlf]

You should not overestimate the quality of such validation. You will be able to catch nonsense like MM=15, DD=42 or DD=30 in February, if the user exchanges values of DD with MM, or types something totally wrong. However, you won't be able to ensure, that the whole date - particularly DD and MM - will be set, as the user intended from an input like 02/05/2018. Was it May 2 or February 2? The user will still have to be aware of the actual format like DD/MM/YYYY. The date picker control usually helps better with ensuring that, than a robuster parser.

[huberzeljko]

Is this an option to validate if date exist?

function validate(date, format) {
  return dayjs(date, format).format(format) === date;
}

validate('2019/02/31', 'YYYY/MM/DD') // false

[YangAi]

Is this an option to validate if date exist?

function validate(date, format) {
  return dayjs(date, format).format(format) === date;
}

validate('2019/02/31', 'YYYY/MM/DD') // false

Thanks! It's very helpful.