27 lines
670 B
Markdown
27 lines
670 B
Markdown
---
|
|
title: unionWith
|
|
tags: array,intermediate
|
|
firstSeen: 2018-01-24T12:19:41+02:00
|
|
lastUpdated: 2020-10-22T20:24:44+03:00
|
|
---
|
|
|
|
Returns every element that exists in any of the two arrays at least once, using a provided comparator function.
|
|
|
|
- Create a `new Set()` with all values of `a` and values in `b` for which the comparator finds no matches in `a`, using `Array.prototype.findIndex()`.
|
|
|
|
```js
|
|
const unionWith = (a, b, comp) =>
|
|
Array.from(
|
|
new Set([...a, ...b.filter(x => a.findIndex(y => comp(x, y)) === -1)])
|
|
);
|
|
```
|
|
|
|
```js
|
|
unionWith(
|
|
[1, 1.2, 1.5, 3, 0],
|
|
[1.9, 3, 0, 3.9],
|
|
(a, b) => Math.round(a) === Math.round(b)
|
|
);
|
|
// [1, 1.2, 1.5, 3, 0, 3.9]
|
|
```
|