30 lines
835 B
Markdown
30 lines
835 B
Markdown
---
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title: uniqueElementsBy
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tags: array,function,intermediate
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---
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Returns all unique values of an array, based on a provided comparator function.
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Use `Array.prototype.reduce()` and `Array.prototype.some()` for an array containing only the first unique occurrence of each value, based on the comparator function, `fn`.
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The comparator function takes two arguments: the values of the two elements being compared.
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```js
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const uniqueElementsBy = (arr, fn) =>
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arr.reduce((acc, v) => {
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if (!acc.some(x => fn(v, x))) acc.push(v);
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return acc;
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}, []);
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```
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```js
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uniqueElementsBy(
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[
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{ id: 0, value: 'a' },
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{ id: 1, value: 'b' },
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{ id: 2, value: 'c' },
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{ id: 1, value: 'd' },
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{ id: 0, value: 'e' }
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],
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(a, b) => a.id == b.id
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); // [ { id: 0, value: 'a' }, { id: 1, value: 'b' }, { id: 2, value: 'c' } ]
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``` |