30 lines
813 B
Markdown
30 lines
813 B
Markdown
---
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title: findLastN
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tags: array,intermediate
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firstSeen: 2021-05-09T13:31:36+03:00
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lastUpdated: 2021-05-09T13:31:36+03:00
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---
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Finds the last `n` elements for which the provided function returns a truthy value.
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- Use a `for` loop to execute the provided `matcher` for each element of `arr`.
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- Use `Array.prototype.unshift()` to prepend elements to the results array and return them if its `length` is equal to `n`.
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```js
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const findLastN = (arr, matcher, n = 1) => {
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let res = [];
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for (let i = arr.length - 1; i >= 0; i--) {
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const el = arr[i];
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const match = matcher(el, i, arr);
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if (match) res.unshift(el);
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if (res.length === n) return res;
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}
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return res;
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};
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```
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```js
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findLastN([1, 2, 4, 6], n => n % 2 === 0, 2); // [4, 6]
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findLastN([1, 2, 4, 6], n => n % 2 === 0, 5); // [2, 4, 6]
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```
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