Proposal: Array.prototype.first() and Array.prototype.last()

Claude Pache claude.pache at gmail.com
Wed Sep 28 06:42:09 UTC 2016


> Le 28 sept. 2016 à 07:38, 段垚 <duanyao at ustc.edu> a écrit :
> 
> Because `foo.bar` is equivlant to `foo['bar']` in JS so far, and `array.-1` could break this consistency.
> 
> 
> On the other hand, `array.first()` seems not necessary because `array[0]` is even more handy; `array.last()` looks fine to me.
> 
> If someone prefer a more general solution, I recommand `array.get(n)`:
> 
>   * if n >= 0 && n < array.length: equivlant to array[n]
>   * if n < 0 && -n < array.length: equivlant to array[array.length + n]
>   * if n <= -array.length || n >= array.length: throw or return undefined
>   * if n is not a integer or not a number: throw or return undefined
> 
> The last 2 rules make `array.get(n)` less error prone than `array[n]`. I prefer throwing, but maybe returning undefined is more JS-style?

For consistency with the rest of the builtin library, `array.get(n)` should be equivalent to `array.slice(n)[0]`, which means: convert `n` to an integer, and: return `undefined` for out-of-bound index.

—Claude

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