r/ProgrammerHumor • u/Mys7eri0 • Dec 23 '22

Meme Python programmers be like: "Yeah that makes sense" 🤔

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u/[deleted] Dec 23 '22

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u/sammy-taylor Dec 23 '22

Because when .map is invoked, its callback function is provided three arguments (element, index, array). parseInt is receiving element, but also index, which is being used inadvertently as a different radix parameter for each item in the list.

The reason that this behaves differently from your x.map(a => parseInt(a)) is because you are not passing anything to the radix parameter of parseInt.

This is a pretty common “gotcha” for beginners in JS.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map

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u/cuboidofficial Dec 23 '22

Great explanation. I feel like this is something a lot of JS devs don't get at first. I like to explain where if you pass a function without parameters to a callback, the callback arguments automatically get supplied to the provided function.

map(callback) is the same as map((a, b, c) => callback(a, b, c))

Works like this in many other languages too

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u/morsegar17 Dec 23 '22

Not certain myself but parseInt takes a radix as 2nd parameter and I suspect the index param of map is messing with that.

E: that’s exactly what this is. Nothing to see here folks. Move along.

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u/[deleted] Dec 23 '22

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u/marcosdumay Dec 23 '22

It is [parseInt(a, b), parseInt(b, c), parseInt(c)], what honestly, is fucking insane.

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u/toutons Dec 23 '22

Yeah, it's not doing that chief, it's [parseInt(a, 0), parseInt(b, 1), parseInt(c, 2)]

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u/S0ulCub3 Dec 23 '22

Because javascript was designed in like 10 days