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Discussion on: Using Python range() in JavaScript

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Replies for: Your code is really weird you mix iterator protocol with generators. You just can use this, it will do the same: function* range(start, stop) { ...

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lionelrowe profile image
lionel-rowe •

Not weird at all, it's a common pattern. That way, you can easily extend your range objects with other properties, like min, max, includes, etc.

More importantly, it also ensures you don't accidentally mutate the range and get unexpected results. With your version:

const r = range(1, 10)
;[...r] // [1, 2, 3, 4, 5, 6, 7, 8, 9], as expected
;[...r] // [], empty array, because the iterator has already been consumed
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With my version:

const r = range(1, 10)
;[...r] // [1, 2, 3, 4, 5, 6, 7, 8, 9], as expected
;[...r] // [1, 2, 3, 4, 5, 6, 7, 8, 9], same as before
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You can still get a mutable iterator from my version if you really need one, though. You just have to ask for it explicitly:

const i = range(1, 10)[Symbol.iterator]()
;[...i] // [1, 2, 3, 4, 5, 6, 7, 8, 9]
;[...i] // []
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