21 lines
714 B
Markdown
21 lines
714 B
Markdown
---
|
|
title: intersectionBy
|
|
tags: array,intermediate
|
|
---
|
|
|
|
Returns the elements that exist in both arrays, after applying the provided function to each array element of both.
|
|
|
|
- Create a `Set` by applying `fn` to all elements in `b`, then use `Array.prototype.filter()` on `a` to only keep elements, which produce values contained in `b` when `fn` is applied to them.
|
|
|
|
```js
|
|
const intersectionBy = (a, b, fn) => {
|
|
const s = new Set(b.map(fn));
|
|
return [...new Set(a)].filter(x => s.has(fn(x)));
|
|
};
|
|
```
|
|
|
|
```js
|
|
intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [2.1]
|
|
intersectionBy([{ title: 'Apple' }, { title: 'Orange' }], [{ title: 'Orange' }, { title: 'Melon' }], x => x.title) // [{ title: 'Orange' }]
|
|
```
|