5 ms·

I know what the batman example gives but I don't get how it's a WTF? I assume the expected output is "wa" but why should a string less an integer produce that?

by hfsktr 12y ago

moron4hire 12y ago
No, it produces NaN (Not-a-Number), and then repeats it in a string 16 times. The WTF is that NaN can be concatenated to strings as "NaN".
- insin 12y ago
  NaN is passed to Array.prototype.join() as the separator to join strings with, so it gets coerced to String ("NaN"). It's deliberately working backward from the behaviour of Array.prototype.join() to create a contrived example for giggles, not a WTF. It's no more a WTF than this, which follows the same principle: https://gist.github.com/insin/1183916 https://gist.github.com/insin/1183916
  - moron4hire 12y ago
    Oh, I understand that. I was more trying to explain why someone might think it was a WTF. And I'm pretty sure your example returns the decimal 15. Comma operator returns the last element in the list, and parseInt will truncate strings with non-number-like text to the number-like part. Here, the number-like part is a hexadecimal code, triggering another feature of parseInt that it can figure out the radix on the fly.
squeaky-clean 12y ago
There is no expected output. It doesn't make sense to subtract the value 1 from the string "wat". But Javascript will cast both of them to numbers, then try to subtract 1 from NaN. However, if you do "wat" + 1, Javascript will cast both of them to strings, and append "1" to "wat". It's not just the odd behavior, but the inconsistency.
- hfsktr 12y ago
  Ok that makes a bit more sense. I didn't even think about how it would be if you tried to add them. I like javascript but I don't do anything so complicated (or maybe not the right types of things) that I run into many of these situations.

5 ms·

I know what the batman example gives but I don't get how it's a WTF? I assume the expected output is "wa" but why should a string less an integer produce that?

by hfsktr 12y ago

I know what the batman example gives but I don't get how it's a WTF? I assume the expected output is "wa" but why should a string less an integer produce that?

moron4hire 12y ago
No, it produces NaN (Not-a-Number), and then repeats it in a string 16 times. The WTF is that NaN can be concatenated to strings as "NaN".
- insin 12y ago
  NaN is passed to Array.prototype.join() as the separator to join strings with, so it gets coerced to String ("NaN"). It's deliberately working backward from the behaviour of Array.prototype.join() to create a contrived example for giggles, not a WTF. It's no more a WTF than this, which follows the same principle: https://gist.github.com/insin/1183916 https://gist.github.com/insin/1183916
  - moron4hire 12y ago
    Oh, I understand that. I was more trying to explain why someone might think it was a WTF. And I'm pretty sure your example returns the decimal 15. Comma operator returns the last element in the list, and parseInt will truncate strings with non-number-like text to the number-like part. Here, the number-like part is a hexadecimal code, triggering another feature of parseInt that it can figure out the radix on the fly.
squeaky-clean 12y ago
There is no expected output. It doesn't make sense to subtract the value 1 from the string "wat". But Javascript will cast both of them to numbers, then try to subtract 1 from NaN. However, if you do "wat" + 1, Javascript will cast both of them to strings, and append "1" to "wat". It's not just the odd behavior, but the inconsistency.
- hfsktr 12y ago
  Ok that makes a bit more sense. I didn't even think about how it would be if you tried to add them. I like javascript but I don't do anything so complicated (or maybe not the right types of things) that I run into many of these situations.