feat: Rework intersect, add overlap

[andreidmt]

Thoughts and proposals on #7 by @dgilperez:

• Current implementation of intersect is misleading. Implemented it as you proposed and as any sane person would expect intersect to behave, return common items.
• I don't like using by default deepEquals so I've created intersectBy to be geared towards object arrays and left intersect with a shallow equals.
• Renamed the previous implementation of intersect as overlap/overlapBy. As I'm writing, union seems a better name for it.
• An important feature of both intersect and overlap is the return of distinct items.

Primary

1. Rework intersect to return common and distinct items from two arrays.
2. Add intersectBy. Allow custom predicate and merge functions, geared towards object arrays.

intersect([1, 2, 3, 3, 4], [3, 3, 4, 5])
// => [3, 4]

intersectBy(
  (a, b) => a.id === b.id,
  (a, b) => ({ ...a, ...b }),
  [
    { id: 1, lorem: "ipsum" },
    { id: 2, foo: "bar" },
  ],
  [
    { id: 2, comments: [] },
    { id: 3, comments: [] },
  ]
)
// => [{ id: 2, foo: "bar", comments: [] }]

3. Add overlap and overlapBy functions to combine two arrays into one with distinct items.

overlap([1, 1, 2, 3, 3], [3, 3, 4, 4, 5])
// => [1, 2, 3, 4, 5]

overlapBy(
  (a, b) => a.id === b.id,
  (a, b) => ({ ...a, ...b }),
  [{ id: 1}, { id: 2 }, { id: 2 }],
  [{ id: 1, foo: "bar" }, { id: 3 }]
)
// => [{ id: 1, foo: "bar" }, { id: 2 }, { id: 3 }]

Secondary

1. Update distinct to use shallow compare.
2. Add distinctBy. Allow custom compare function, geared towards object arrays.

// old
distinct([1, {a: 2}, {a: 2}])
// => [1, {a: 2}]

// new
import deepEquals from "fast-deep-equal"

distinctBy(deepEquals, [1, { a: 2 }, { a: 2 }])
// => [1, {a: 2}]

Checklist

• Tests
• JSDocs
• Export in src/index.js

[andreidmt]

Hey @dgilperez, added this PR based on your #7 proposal.

Waiting for your thought and can continue with difference after we finish with these.

[dgilperez]

Hey, sorry for the delay @andreidmt

The changes on intersect and distinct make a lot of sense in my opinion.

Otoh, I think overlap is a confusing term - for me, overlap is almost a synonym for intersection. I'd argue the proposed implementation for overlap is actually a join. If we go to SQL joins, there are a number of different joins of course (left, right, inner, outer ...), adding to the confusion, but in general terms I think is a better term for this operation.

[andreidmt]

I like the idea of syncing the naming with SQL operations (where applicable). Renamed "overlap" -> "join" and the old join to "unite".

[andreidmt]

🎉 This PR is included in version 6.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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