this post was submitted on 16 Jun 2023
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[–] [email protected] 2 points 1 year ago

POV: you don't understand type coercion

[–] [email protected] 1 points 1 year ago
[–] [email protected] 1 points 1 year ago* (last edited 1 year ago) (1 children)

This one is one of my favourite JS quirks:

JS quirk

[–] [email protected] 0 points 1 year ago (1 children)

Wait wtf is happening there?

[–] [email protected] 1 points 1 year ago

parseInt is meant for strings so it converts the number there into a string. Once the numbers get small enough it starts representing it with scientific notation. So 0.0000001 converts into "1e-7" where it then starts to ignore the e-7 part because that's not a valid int, so it is left with 1

https://javascript.plainenglish.io/why-parseint-0-0000001-0-8fe1aec15d8b

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago) (1 children)

Ok some of these I understand but what the fuck. Why.

Edit: ok I have a theory. == checks equality without casting to any types, so they're not equal. But < and > are numeric operations, so null gets cast to 0. So <= and >= cast it to 0, and it's equal to 0, so it's true.

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago)

I'm not sure if you really want to know, but:

greater than, smaller than, will cast the type so it will be 0>0 which is false, ofcourse. 0>=0 is true.

Now == will first compare types, they are different types so it's false.

Also I'm a JavaScript Dev and if I ever see someone I work with use these kind of hacks I'm never working together with them again unless they apologize a lot and wash their dirty typing hands with.. acid? :-)

edit: as several people already pointed out, my answer is not accurate. The real solution was mentioned by mycus

[–] [email protected] 0 points 1 year ago (1 children)

Can someone explain this? I mean, the last result. Usually I can at least understand Javascript's or PHP's quirks. But this time I'm stumped.

[–] [email protected] 0 points 1 year ago (1 children)

JS null and undefined shenanigans


basically:

  1. bigger an lesser comparison types convert null to zero, so is zero bigger or lesser than zero? no
  2. == is fucky and to it null only equals undefined and undefined only equals null (and themselves), so no
  3. is zero bigger than or equal to zero? yeah
[–] [email protected] 0 points 1 year ago (1 children)

Ugh, thanks, of course. Stupid brain.

[–] [email protected] 0 points 1 year ago (1 children)

I'm starting to think JS maintainers have a thing against mathematicians

[–] [email protected] 1 points 1 year ago

more likely against humans

[–] [email protected] 0 points 1 year ago (1 children)

I know it’s a joke, but it’s an old one and it doesn’t make a lot of sense in this day and age.

Why are you comparing null to numbers? Shouldn’t you be assuring your values are valid first? Why are you using the “cast everything to the type you see fit and compare” operator?

Other languages would simply fail. Once more JavaScript greatest sin is not throwing an exception when you ask it to do things that don’t make sense.

[–] [email protected] 1 points 1 year ago

Shouldn’t you be assuring your values are valid first?

Step 1: Get to prod

Step 2-10: Add features

Step 11: Sell the company before it bites you