CODEWITHSUNDEEP
javascript
Alex Krupka
Alex Krupka

Reputation: 730

How to validate a date based on a format string in JS

I want to check whether a date is valid given a given format in JavaScript. In essence I'd like to see of a string can be parsed to the given format. Since Date.parse doesnt take a format string i can't figure out how to do this

Date.parse('01/21/2017','dd/mm/yyyy') //should return null
Date.parse('21/01/2017','dd/mm/yyyy') //should return date

Upvotes: 0

Views: 541

Answers (3)

Vladu Ionut
Vladu Ionut

Reputation: 8193

Date.parse(dateString) method has only one parameter

dateString - accept a string representing an RFC2822 or ISO 8601 date format (other formats may be used, but results may be unexpected ")

To parse and validate a string you can use an external library like moment.js .

console.log(moment('01/21/2017', 'DD/MM/YYYY', true).isValid());
console.log(moment('21/01/2017', 'DD/MM/YYYY', true).isValid());
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.17.1/moment.js"></script>

Upvotes: 1

Nikhilesh Shivarathri
Nikhilesh Shivarathri

Reputation: 1670

I do not think this is a proper use case of validating it with the format.

Because

  1. Consider the use case of date 3rd April 2017 that would be 03/04/2017 in dd/mm/yyyy format and 04/03/2017 in mm/dd/yyyy format.

Now if you consider validating this scenario, you never know what the input actually meant it might be 3rd April 2017 or 4th March 2017 in your scenario.

  1. Even if you want to consider the hard way of getting the validation, then you can use Date constructor. For example

Consider date 23rd March 2017.

Now try new Date('23/03/2017') This would return you null. Javascript date returns you date object if the input was correct, i.e., it is expecting yyyy/mm/dd or mm/dd/yyyy

console.log(new Date('23/03/2017'));

  1. Use External libraries like moment.js which has some decent functions like comparing them with the format of the date input. 

var x = '03/23/2017';

console.log(moment(x, 'DD/MM/YYYY', true).isValid());

console.log(moment(x, 'MM/DD/YYYY', true).isValid());
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.17.1/moment.min.js"></script>

hope this helps you!

Upvotes: 3

Vaibhav Bansal
Vaibhav Bansal

Reputation: 346

If its possible to use moment.js, you can do something like

function parseDate(dateString, format){
 if (moment(dateString,format).isValid())
  return moment(dateString, format).toDate();
 else
  return null;
}

Upvotes: 2

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