This condition returns a boolean when checking for a falsy, but it returns a string when checking for a truthy value. How can I get it to work?

Question

I get a boolean return when checking for a falsy value, but not a boolean when checking for a truthy value... I am just getting a string instead.

This works.

const isFalse = !values.firstName && !values.lastName && !values.email;

But this doesn't, as I get returned a string only.

const isValid = values.firstName && values.lastName && values.email;

Although, I can achieve the desired result with the following... It doesn't seem the best way forward.

const isValid = values.firstName && values.lastName && values.email ? true : false;

How would I be able to check the string for a truthy value and get boolean as a result (instead of a string)?

Does this answer your question? [Why don't logical operators (&& and ||) always return a boolean result?](https://stackoverflow.com/questions/5417969/why-dont-logical-operators-and-always-return-a-boolean-result) (Check the highest voted answer, _not_ the accepted answer.) — Ivar, Sep 14 '20 at 11:35
`!` does not turn a truthy value into a falsy value, it turns a truthy value into `false` and a falsy value into `true` — Jonas Wilms, Sep 14 '20 at 11:38

Grateful · Answer 1 · 2020-09-14T12:21:53.517

1

Wow, that was quick. I found out that you can do a double negative to achieve the same result and get it to work!! (pun intended)

const isValid = !!(values.firstName && values.lastName && values.email);

edited Sep 14 '20 at 12:21

answered Sep 14 '20 at 11:37

Grateful

While this is correct, it does not answer **Why does this javascript condition return a boolean when checking for a falsy string value, but return a string when checking for a truthy value?**. – Lain Sep 14 '20 at 12:10
I've edited the question to reflect what I was actually looking for as an answer. Thank you nonetheless. – Grateful Sep 14 '20 at 12:19
I see. What you basically want to do is `values.every((v) => v)` or `['g', 'r', '@'].every((v) => v)`. [every](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/every). – Lain Sep 14 '20 at 12:27
@Lain Umm... Thank you for sharing about 'every'... But it is an overkill for what I need. So the two negatives will suffice, thank you. – Grateful Sep 14 '20 at 12:29

score -2 · Answer 2 · answered Sep 14 '20 at 11:38

-2

Well, Javascript can be weird sometimes... I don't know exactly why it happens, but I can tell you how to get a boolean value:

const isValid = !!values.firstName && !!values.lastName && !!values.email;

answered Sep 14 '20 at 11:38

xurei

Thank you for your participation. I chanced upon the answer in parallel. – Grateful Sep 14 '20 at 11:40
Well apparently someone doesn't like this answer... – xurei Sep 14 '20 at 11:42
I am sorry about that buddy, but it wasn't me. Someone apparently doesn't like my question either. :) – Grateful Sep 14 '20 at 11:44
@Grateful Uhh, your question has an upvote (and no downvotes)? – Ivar Sep 14 '20 at 11:45
@xurei Beats me... They just closed the question. In any case, with "privileged trigger-happy people", the place can be weird sometimes. Over the years, I have learnt to take what I need and get outta here. :) – Grateful Sep 14 '20 at 11:47
@Grateful yeah this is sad. I probably should have flagged your question as a duplicate. Not very welcoming IMO. Thanks for the upvote, Karma is balanced again ^_^ – xurei Sep 14 '20 at 11:51
@xurei Although, the downvotes are probably due to the unrelated "bonus" that you provided towards the end. – Grateful Sep 14 '20 at 12:34

2 Answers2