38 lines
1.0 KiB
Markdown
38 lines
1.0 KiB
Markdown
---
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title: Ungroup array elements based on function
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type: snippet
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language: javascript
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tags: [array]
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cover: rustic-cup
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dateModified: 2022-01-23T13:18:50+03:00
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---
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Creates an array of elements, ungrouping the elements in an array produced by [zip](/js/s/zip) and applying the provided function.
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- Use `Math.max()` and the spread operator (`...`) to get the longest subarray in the array, `Array.prototype.map()` to make each element an array.
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- Use `Array.prototype.reduce()` and `Array.prototype.forEach()` to map grouped values to individual arrays.
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- Use `Array.prototype.map()` and the spread operator (`...`) to apply `fn` to each individual group of elements.
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```js
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const unzipWith = (arr, fn) =>
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arr
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.reduce(
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(acc, val) => (val.forEach((v, i) => acc[i].push(v)), acc),
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Array.from({
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length: Math.max(...arr.map(x => x.length))
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}).map(x => [])
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)
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.map(val => fn(...val));
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```
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```js
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unzipWith(
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[
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[1, 10, 100],
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[2, 20, 200],
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],
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(...args) => args.reduce((acc, v) => acc + v, 0)
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);
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// [3, 30, 300]
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```
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