Add selectors

[ryoid]

Using createSelector is good for a single values. I found that there are a lot of use cases for array selectors. I have been using this on a few projects and I think it would be a good addition to the library.

const list: string[] = ["apple", "pear", "orange"]
const [selectedItems] = createSignal<string[]>(["apple"])
const isSelected = createArraySelector(selectedItems)

<For each={list}>
  {(item) => <li classList={{ active: isSelected(item) }}>{item}</li>}
</For>

Extending with a comparator function (instead of b.includes(a)) to support objects could be possible, but I decided to keep it simple. At that point it might be better to just create a custom selector directly.

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[thetarnav]

It's an interesting idea to have a package dedicated to the selector primitive. There might be other helpers this could include.
But right now I wouldn't advice anyone to use it with only createArraySelector, especially when it doesn't provide too much value.
Also I'm wondering if instead of exporting a createSelector wrapper, it would be better to just export the (key, list) => list.includes(key) part. Then one could compose it with the selector.

import { arrayIncludes } from "@solid-primitives/selector"

const isItemSelected = createSelector(selectedItems, arrayIncludes)

[thetarnav]

it should allow readonly arrays too

Suggested change

	source: () => Array<T>,
	source: () => readonly T[],

[thetarnav]

Better to reuse types from solid for the options (and any other type if possible), to show where it is coming from, and remove the need for updating the types when options in solid change.

[thetarnav]

prefer selector singular to match the rest of the packages

[thetarnav]

Worth adding that it doesn't work when mutating the array:
https://playground.solidjs.com/anonymous/bfeda055-2f2c-465e-b438-ea9d671a4eb8

[thetarnav]

Worth showing that the implementation is basically an alias to createSelector with Array.includes

const createArraySelector = source => createSelector(source, (key, list) => list.includes(key))

I don't want anyone to get an impression that it's not possible to do this with createSelector