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fix: differenceBy.md --> update differenceBy.test.js

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This commit is contained in:
Bejamin Schachter
2019-03-05 12:26:06 -05:00
parent 13717dbb42
commit 675d281422
2 changed files with 6 additions and 6 deletions
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8
snippets/differenceBy.md
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@ -2,16 +2,16 @@
Returns the difference between two arrays, after applying the provided function to each array element of both.
Create a `Set` by applying `fn` to each element in `b`, then use `Array.prototype.filter()` in combination with `fn` on `a` to only keep values not contained in the previously created set.
Create a `Set` by applying `fn` to each element in `b`, then use `Array.prototype.map()` to apply `fn` to each element in `a`, then `Array.prototype.filter()`
```js
const differenceBy = (a, b, fn) => {
const s = new Set(b.map(fn));
return a.filter(x => !s.has(fn(x)));
return a.map(fn).filter(el => !s.has(el));
};
```
```js
differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1.2]
differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [ { x: 2 } ]
differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1]
differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [2]
```

4
test/differenceBy.test.js
View File

@ -5,8 +5,8 @@ test('differenceBy is a Function', () => {
expect(differenceBy).toBeInstanceOf(Function);
});
test('Works using a native function and numbers', () => {
expect(differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor)).toEqual([1.2]);
expect(differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor)).toEqual([1]);
});
test('Works with arrow function and objects', () => {
expect(differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x)).toEqual([{ x: 2 }]);
expect(differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x)).toEqual([2]);
});