Comparing two times with Moment JS

Question

I have a problem that requires me to take two times in 12 hour format and compare them, we have moment.js included in our project and we initially thought it would be as trivial as this:

var beginningTime = moment('8:45am');
var endTime = moment('9:00am');
console.log(beginningTime.isBefore(endTime)); //false???

Fiddle: http://jsfiddle.net/KyleMuir/M4R4z/

Is there something we are missing? It feels like this shouldn't be a hard problem to solve. When we perform any moment functions on our beginningTime or endTime it simply says NAN

Answer 1

If you are always dealing with the time in h:mma format, you can specify it when parsing...

var beginningTime = moment('8:45am', 'h:mma');
var endTime = moment('9:00am', 'h:mma');
console.log(beginningTime.isBefore(endTime)); // true
console.log(beginningTime.toDate()); // Mon May 12 2014 08:45:00
console.log(endTime.toDate()); // Mon May 12 2014 09:00:00

<script src="https://cdn.jsdelivr.net/momentjs/2.13.0/moment.min.js"></script>

It will use today as the date, so it won't work if you are spanning different days.

JSFiddle

Answer 2

As per documentation you are declaring moment variable incorrectly check allowed formates

http://momentjs.com/docs/#/parsing/string/

Instead of it you can use

var beginningTime = moment({
  h: 8,
  s: 45
});
var endTime = moment({
  h: 9,
  s: 0
});
console.log(beginningTime.isBefore(endTime)); //true

<script src="https://cdn.jsdelivr.net/momentjs/2.13.0/moment.min.js"></script>

Answer 3

8:45am and 9:00am are invalid dates

var beginningTime = moment('8:45am');
var endTime = moment('9:00am');
console.log(beginningTime.isValid(), endTime.isValid()) // FALSE

You should use a valid format: http://momentjs.com/docs/#/parsing/string/

And they suggest that for consistent results, should use http://momentjs.com/docs/#/parsing/string-format/

Eg.

moment("2010-10-20 4:30", "YYYY-MM-DD HH:mm"); // parsed as 4:30 local time

Answer 4

You should just open the console and try doing this manually: moment("8:45am").toDate()

It gives you Invalid Date, which is why you're not getting expected results. Whereas "2014-05-15 08:45" gives you a date.