22 lines
559 B
Markdown
22 lines
559 B
Markdown
---
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title: Check if all array elements are unique
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tags: array
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cover: jars-on-shelf
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firstSeen: 2020-10-19T19:47:26+03:00
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lastUpdated: 2021-01-08T00:23:44+02:00
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---
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Checks if all elements in an array are unique.
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- Create a new `Set` from the mapped values to keep only unique occurrences.
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- Use `Array.prototype.length` and `Set.prototype.size` to compare the length of the unique values to the original array.
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```js
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const allUnique = arr => arr.length === new Set(arr).size;
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```
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```js
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allUnique([1, 2, 3, 4]); // true
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allUnique([1, 1, 2, 3]); // false
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```
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