4 ms·

I didn't know about the second parameter until I saw it in a TypeScript signature a few months ago, which acted as a sort of warning to me to avoid using it inc

I didn't know about the second parameter until I saw it in a TypeScript signature a few months ago, which acted as a sort of warning to me to avoid using it incorrectly. But TypeScript doesn't catch this specific bug because it's technically correct[1] from an API stand-point, as the second parameter to parseInt is a number and the second argument to map's callback is a number. For as many situations as TypeScript genuinely helps you, there are just as many situations where it gives you false security, like in this case, and I'm starting to consider not using it anymore. [2] [1] not actually "the best kind of correct" despite popular television quotes [2] https://sdegutis.com/2019-06-20-considering-removing-typescript https://sdegutis.com/2019-06-20-considering-removing-typescr...

carlmr 7y ago
Yeah, the problem this one time isn't typing but the JS developers implementing map wrong. Map should not take two arguments. There should be a different function like enumerate in in python for this.
- sdegutis 7y ago
  There's nothing wrong with Array#map passing callback(val, i, array), it's a legitimate feature, and the two other arguments can be omitted in actual callbacks. It just means we need to be aware of how it works, which is basically true about any programming language, any standard library, and basically any kind of tool that any kind of professional uses, whether abstract or literal: know how to use your own tools, and avoid blaming the wrench because it's a poor excuse for a hammer.
  - acdha 7y ago
    > know how to use your own tools, and avoid blaming the wrench because it's a poor excuse for a hammer This is, of course, why famously machine shops simply put up signs saying “don't touch the whirring metal” rather than using safety guards and similar measures. I don't disagree that it's useful to have the extra arguments for map but the part which is really deadly is ignoring extra arguments, even if it's obvious why backwards-compatibility made changing it unlikely. I really wish that JavaScript had implemented keyword-arguments when the benefits had become obvious because when features like map were added a decade or two later they could have been defined as passing arguments by keyword and causing an error when given a function which didn't accept those names.

carlmr 7y ago

Yeah, the problem this one time isn't typing but the JS developers implementing map wrong. Map should not take two arguments. There should be a different function like enumerate in in python for this.

sdegutis 7y ago
There's nothing wrong with Array#map passing callback(val, i, array), it's a legitimate feature, and the two other arguments can be omitted in actual callbacks. It just means we need to be aware of how it works, which is basically true about any programming language, any standard library, and basically any kind of tool that any kind of professional uses, whether abstract or literal: know how to use your own tools, and avoid blaming the wrench because it's a poor excuse for a hammer.
- acdha 7y ago
  > know how to use your own tools, and avoid blaming the wrench because it's a poor excuse for a hammer This is, of course, why famously machine shops simply put up signs saying “don't touch the whirring metal” rather than using safety guards and similar measures. I don't disagree that it's useful to have the extra arguments for map but the part which is really deadly is ignoring extra arguments, even if it's obvious why backwards-compatibility made changing it unlikely. I really wish that JavaScript had implemented keyword-arguments when the benefits had become obvious because when features like map were added a decade or two later they could have been defined as passing arguments by keyword and causing an error when given a function which didn't accept those names.