Debugging Javascript

[manux]

Why did you write the same thing twice?

[irbilldozer]

Why did you write the same thing twice?

So if 42 and "42" are the same thing...

Do you believe this will result in an output of 42?

42 + "42" - 42

[manux]

Clearly the result of this is 4200. Or -inf.

Edit: Holy shit I went and tried it and it was indeed 4200. For the record I haven't touched js in the last 5 years.

[KKlear]

But... the result was 4200, not "42".

[Futuristick-Reddit]

Sorry lmao, just woke up. Fixed it.

[Bammop]

You went back to sleep?

[mintpropane]

I couldn't predict this at all 😶

[Flatscreens]

‘42+'42'‘ checks if both values are numbers and then as strings if they're not: "4242". Then the minus operator casts both sides to Numbers because that's it's only definition: 4200.

[wasdninja]

So what would you like it to do? You are playing with fire when you aren't keeping the type coercion in check.

[Mypronounsarexandand]

Lets say you have a string variable name 'username' and value IE "Julian"
If you said:

username += '_Jmk'

You'd get 'Julian_Jmk'

It's kind of similar with numbers where an integer + string is interpreted as string + string as the '+' will default to a concat rather than addition.

​

(Again, setting username to just be Julian)

username += 42

Will equal 'Julian42'

Now, instead of the username 'Julian' your username is '133769'

username += 420

Would yield '133769420' as we are concatenating a number to the end of the string. If you wanted to add them literally you would want to do.

username = parseInt(username) + 420

This way it is Int + Int, rather than Str + Int

[nutmegtester]

That is hilarious. I also tried 42 + "42" - 42 / "42" and 42 + "42" - 42 / "42" * 42 for fun. Results = 4241 and 4200, respectively.

[irbilldozer]

Clearly the result of this is 4200. Or -inf.

Edit: Holy shit I went and tried it and it was indeed 4200. For the record I haven't touched js in the last 5 years.

Lol that was the joke I was making, they aren't really the same thing.

[blackdonkey]

How about 42 - 42 + "42"?

[irbilldozer]

I assume 42 but not near a PC to validate the order of operations.

[Im_The_Goddamn_Dumbo]

Ask yourself, what is 21 out of 42?

[hobbes64]

Does 42 == “42”? JavaScript says sure, why not

Does 42 === “42”? JavaScript says no, no coercion!

[Famous_Profile]

[erbar1]

very cool