flatMap or flatten

[Frankie Bagnardi]

I often do the `.reduce((xs, ys) => xs.concat(ys))` and I feel the need to
leave a comment explaining what it does.

+1 to this proposal.


On Fri, May 19, 2017 at 12:44 PM, Luan Nico <luannico27+es-discuss at gmail.com
> wrote:

> I always surprise myself finding out there's no native way to flat an
> array. I know it's easy to implement, but to increase legibility I propose
> creating one of two options (either suffice, I believe):
>
>   - `flatMap` : regular map, but flattens the array afterwards
>   - `flatten` : just call on an array and get a new flattened array
>
> Some examples usages of both:
>
> With `flatMap`:
> ```
>     const numbers = [12, 35];
>     const divisors = numbers.flatMap(factors);
> ```
>
> With `flatten`:
> ```
>     const numbers = [12, 35];
>     const divisors = numbers.map(factors).flatten();
> ```
>
> Flattening an array is converting something like `[1, [2, 3], 4]` to `[1,
> 2, 3, 4]`.
> There is also need to choose whether it's deep or shallow.
>
> I suggest adding a `flatten` shallow method, as that would be useful in
> all scenarios described.
>
> Example implementation:
>
> ```
>     Array.prototype.flatten = function () {
>         return [].concat.apply([], this);
>     };
> ```
>
> What are your opinions about it?
>
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