feat(head): add optional n elements parameter

[danielbayley]

For example:

const array = [1, 2, 3, 4]

_.head(array, { n: 2 }) // [1, 2]
// or
_.first(array, { n: 2 }) // [1, 2]

_.head(array) // 1

[array].map(_.head) // [1]

[Trott]

I imagine this breaks usage of .head() as a callback with Array.prototype.map() and similar functions. map() sends the index of the array as the second argument to the callback. With this change, that will now affect how many elements are returned.

[Trott]

Currently, head() always returns the first element.

With this change, head([0,1], 500) returns an array, but head([1], 500) returns 1. Seems like a footgun.

[danielbayley]

I imagine this breaks usage of .head() as a callback with Array.prototype.map() and similar functions. map() sends the index of the array as the second argument to the callback. With this change, that will now affect how many elements are returned.

@Trott Fair point. My first contribution to this project, so not entirely sure what the design goal specifics are… But my assumption was that pure functional methods—with strict arity—were for lodash/fp?

Anyway, just pushed a fix to avoid said potential foot injuries!

An alternative approach might be to have something like headN/firstN additional methods…

[Trott]

My first contribution to this project, so not entirely sure what the design goal specifics are… But my assumption was that pure functional methods—with strict arity—were for lodash/fp?

Yeah, I'm not a maintainer or even much involved in lodash whatsoever. So feel free to disregard for the reasons you state and await a review from a project member.