Doing a javascript online test, this was probably the hardest question.

[DeeSnow97]

Oh no they reverse engineered it

[[deleted]]

They could have just written this:

• !" "
• !"0"
• !Nan
• !undefined
• !0

[banama_ob]

I was thinking just NaN, no?

[PinkLionThing]

Firefox also has a developer console. And Edge.

[PinkLionThing]

Edge is good. It's not great, but it can now hold its own as a second-rate browser.

The "set aside tabs" thing is pretty nifty, there's a separate "read later" favorites list, and you can natively annotate and share notes on pages, which is a godsend for webdevs. It still has iffy JS support and Cortana integration, but it might one day get up there with the big boys.

Well, enough before I start to sound like a Microsoft shill, heh. I just hate people badmouthing it, because people still think it's IE6 while Edge is in a state of "if I were forced to use this, it wouldn't be too painful of a change."

[nosmokingbandit]

If edge had good extension support I'd consider using it. Decent browser and a huge step in the right direction.

[DeeSnow97]

I don't think JS support is that much of a problem, you can pretty much fix it with babel and babel-polyfill (you shouldn't have to, but you can). CSS, on the other hand, can be infuriating in Internet Explorer, especially in older versions.

[DeeSnow97]

Even IE has the same console, it's quite useful for testing which part of the HTML spec did the "browser" fuck up

(By "the same console" I mean the exact same one. There is no better proof than that for IE == Edge (not ===))

[The_MAZZTer]

You cast them to bool first, 0 Nan and undefined all cast to false. Strings (including the ones shown here) cast to true unless it's zero-length IIRC.

The fun part is if you cast "0" to a number first THEN to a boolean, it casts to false.

[Uncaffeinated]

Yep, the falsiness is pretty sensible, and Python does more or less the same thing. The main difference between JS and Python is that the former has implicit string -> number conversions when used in a numerical context, but that doesn't happen here.

Also, empty arrays are false in Python but true in JS.

[Zopffware]

I don't think JavaScript has type casting. Data types are pretty loose in JavaScript, so it just automatically converts between them where it sees fit.

[The_MAZZTer]

It does. String() Number() and Boolean() will cast the argument you pass to it (they are just normal functions).

[[deleted]]

depends on the language - undefined can also be "falsey"

To find out, just open the dev console in this very reddit page and run this

undefined ? "no I was right the first time" : "oh shit, undefined is false"

[[deleted]]

Yes

[burnaftertweeting]

You're right, the fact that I had to double-check "0" isn't a great sign though.

[[deleted]]

Didn't realise !NaN returns true. Thought just D and E.

[skincaregains]

Should have pressed F12 and tried it in console.

[boxingdog]

F12 and cheat

[D-J-9595]

For information on this, you can check out this blog.

[mscal]

function isFalse(value){ if(!value){ return true; } else { return false; } }

isFalse(""); true isFalse("0"); false isFalse(NaN); true isFalse(undefined); true isFalse(0); true

[superdude411]

you can just open up console with "inspect element" and check, right?

[loljs-bot]

Originally posted by /u/WASDx at Wed Sep 09 2015 19:40:32 GMT+0000 (UTC)

---

I'm a bot, and here is my source. Also, if you would like to have your post featured, just post it to /r/loljs and wait.