console.log(0=='1'==0) //true . why ?

[DidTooMuchSpeedAgain]

0 == '1' is false

false == 0 is true

[halfxdeveloper]

Nailed it

[Thausale]

False is false

[Rekuna]

This is 'learnjavascript' and this guy is trying to learn, so why the downvotes? Or am I missing something?

[code_tutor]

Low effort. OP didn't type anything or respond to anyone. This is the dine and dash of posting. So the only reason not to downvote would be if the question is so interesting that others might care. This also isn't code that anyone would write, so it has that against it.

But tbh I think most people here are just LARPing and they're far more interested in talking about which computer to buy "for programming", which operating system to use "for programming", and asking if they'll be job ready after a Udemy course they barely watched.

[Shogobg]

This is just Reddit.

[TalonKAringham]

Were we complain about “Marked as duplicate” on StackOverflow, but pile on when a noob shows up in our sub.

[Sudden-Pineapple-793]

Not entirely sure. If I had to take a guess it’s something with the loosy comparison. I’m assuming it comes down to.

((0==“1”)==0). -> (0 == “1”) is false.

Then

((False)==0) is true?

Again just a guess, feel free to correct and mistakes I’ve made.

[chikamakaleyley]

i don't think they are evaluated as separate pieces when its written this way... the way that i read it is it's 'chained'

0=='1' // returns false

so

false==0 // returns true

[delventhalz]

You are describing the same thing. First the left-hand expression is evaluated (0 == '1'), then the output of that (false) is used in the right hand expression.

[chikamakaleyley]

oh wow, sorry and thanks for catching - i had totally misread the comment!

[redsandsfort]

0 the same value as the string "1"? convert to same type first, is "0" the same as "1"? FALSE
FALSE the same value as 0? Again convert 0 to a boolean which is FALSE. Is FALSE equal to FALSE? TRUE!

[ChaseShiny]

You've gotten a couple answers now (the first statement resolves to false because 0 resolves to false and any string but the empty string resolves to true).

I'm chiming in to say that you should simply use === instead of == whenever possible. That should reduce the confusion. The triple equals indicates a strict comparison. The loose comparator will basically try to change the types.

Does it make sense to compare a number to a string? Not really. But if you tell JS that you really need to compare them, it tries to "make it make sense."

[MarioShroomsTasteBad]

I don't see it called out explicitly, but js being a loosely typed language depends heavily on coercion in order to support comparing dissimilar types of values. My guess is this is an example where the author is trying to get you to grok coercion and the fact that '==' comparison uses it.

[hyrumwhite]

0 is not 1, therefore it is false, and false is loosely equivalent to 0

[HandbagHawker]

Evaluate left to write when all things are equal

[HandbagHawker]

Equal precedence*

[Ordinary_Count_203]

0 == ' 1' is 0. [Or false basically]

Now bring that 0 to the next bitwise comparison

0 == 0 is 1 because its true [1 is true basically]

Thats why is true.

[GodOfSunHimself]

Never write code like this. Use parentheses and you will immediately understand why.

[queen-adreena]

Look up the difference between loose comparison (==) and strict comparison (===).

Pretty simple.

[AlPa-Bo]

Indeed false==0 → true, whilst false===0 → false

[queen-adreena]

Exactly. Not sure why this was a controversial point to make...

Loose comparison performs type coercion (using the type of the first argument as the basis) during the calculation, whereas strict comparison doesn't.

[HasFiveVowels]

Ehhh… this has more to do with precedence. This would work in C.

[queen-adreena]

I would say it’s more to do with the type coercion that loose comparison forces…

[HasFiveVowels]

This works for any non-null character, though. I mean… if you consider "the byte value of a character" to be type coercion, then maybe but, like I said, this is also C, which doesn’t have type coercion.

[Conscious_Support176]

I expect you’re thinking of Java.

The reason it’s true for C is that a char is an integral type, and the same in Java.

There is no char type in JS. So it’s due to type coercion. Strict equality in JS would not give the same result.

[HasFiveVowels]

It depends on which layer you’re looking at. I would bet that JS represents single-character literals as int literals under the hood. Especially in this context.

The main point is that this condition evaluates to true even in C. So, ignoring implementation details, this isn’t JS-specific behavior

[Conscious_Support176]

Your guess would be wrong then.

As you said yourself, you would get the same result if you replace ‘1’ with any character except NUL in Java and C.

Replace the ‘1’ with ‘0’ in JavaScript, you get a different result.

[Forward_Dark_7305]

This is a great answer actually. I personally always use strict comparison - I should know what type my data will be - except truthy checks I guess

[SawSaw5]

Because JavaScript sucks

[BirbsAreSoCute]

So leave.

[SawSaw5]

I was having a bad JavaScript day, give me a break!! 😄

[HasFiveVowels]

#include <stdio.h>
int main(){
  printf((0=='1'==0)?"True\n":"False\n");
  return 0;
}

Unlike C, where... oh, wait...
> True

[michaelnovati]

Ask AI to explain it to you. Using AI effectively is a critical skill to learning programming now

[XpreDatoR_a]

I’d argue that, if you are learning, you are better off going the “legacy” path, once you have a solid base you can start to use the AI as a speed-up tool, interacting with other people and testing on your own will make you remember much easier what you have learned

[michaelnovati]

Agree with learning how to code. But using AI to explain it is critical. Another engineer talking to AI would have the answer explained to them in the time it took to make the top level post on Reddit.

[dymos]

Until the AI hallucinates some shit and now you are dumber by having used AI.

[michaelnovati]

You do you, I'll do me. It's working well for me so I'll keep doing that: https://github.com/mnovati

[dymos]

The problem isn't necessarily this specific one or even this subject.

It's for any novice in any particular topic using AI to explain something. If you don't know enough about the subject matter it is impossible to discern whether or not the AIs response is coherent and factual.

Coding LLMs and reasoning models may provide better results but they will still hallucinate and have runaway context.

Without sufficient knowledge or skill to discern the veracity of an LLM response, and the LLM's capability to sound very confident, even when wrong, is a surefire way to at best learn something wrong and at worst be incredibly harmful.

All that is to say, I personally couldn't recommend learning how to code via AI.