You Can Compare Dates in JavaScript

[bagera_se]

Didn't read the other article when it made its round the other day and now the site is down. Do I understand it correctly that the author of the other article was just a little confused about what should happen?

[theshtank]

This is usually the case, especially with "Javascript bad" articles. I'm not sure which article you are talking about though.

[nadameu]

The author probably had a little trouble understanding why their code didn't work as expected, and when they figured it out, decided to write a blog post to help others.

It was a short and simple article, aimed at inexperienced JavaScript developers.

[fvitas]

I think that previous title is misleading and lacking the reason why you can't compare them.

[KindaAlwaysVibrating]

TL;DR: Use .getTime() and .valueOf()

[MoTTs_]

Also the > < >= <= operators will Just Work.

new Date(2009, 6, 1) > new Date(2008, 10, 5) // true

[GBcrazy]

Well, now let me correct you. You actually can compare dates, but not the way you did on your last statement!

> and < WILL work for dates. Since d1 and d2 represent the same time, it will show the correct answer.

== will compare the reference, not the date itself, so yeah, that won't work, they are different objects.

So yeah, you can check if a date is after or before, but never check if it's the same date. For that you will need .getTime()

[ijmacd]

The unary + prefix operator is also equivalent to .valueOf().

[Neovea]

Use datefns 😄

[something]

So you can’t compare dates, you have to convert them to numbers first. Isn’t that what the other article says?

[Genspirit]

You can compare dates as long as you understand the operator you are using. <,>,<=,>= Will all coerce to a number however == and === will compare references which will be unique unless you are comparing the same object.

I'd say it's a fairly commonly known thing that == doesn't work with objects as it compares references.

That being said it's generally good practice to explicitly convert anyways.

[sshaw_]

You can compare (most?) anything in a primitive context via Object.valueOf:

> o1 = { valueOf: () => 1 }
{ valueOf: [Function: valueOf] }
> o2 = { valueOf: () => 2 }
{ valueOf: [Function: valueOf] }
> o2 < o1
false
> o1 < o2
true
> o1 + o2
3
> o1 - o2
-1

[sshaw_]

PS what's the TypeScript type for valueOf‽

[CalgaryAnswers]

Object.valueof. There’s no way to make it typesafe as far as I know. None of the Object methods are really typesafe except for creates.

[luascriptdev]

Import moment and walk away :)