24 lines
554 B
Markdown
24 lines
554 B
Markdown
---
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title: Array difference
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tags: array
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cover: interior-3
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firstSeen: 2017-12-17T16:41:31+02:00
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lastUpdated: 2020-10-19T18:51:03+03:00
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---
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Calculates the difference between two arrays, without filtering duplicate values.
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- Create a `Set` from `b` to get the unique values in `b`.
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- Use `Array.prototype.filter()` on `a` to only keep values not contained in `b`, using `Set.prototype.has()`.
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```js
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const difference = (a, b) => {
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const s = new Set(b);
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return a.filter(x => !s.has(x));
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};
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```
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```js
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difference([1, 2, 3, 3], [1, 2, 4]); // [3, 3]
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```
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