14 lines
557 B
Markdown
14 lines
557 B
Markdown
### Flatten array up to depth
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Use recursion, decrementing `depth` by 1 for each level of depth.
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Use `Array.reduce()` and `Array.concat()` to merge elements or arrays.
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Base case, for `depth` equal to `1` stops recursion.
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Omit the second element, `depth` to flatten only to a depth of `1` (single flatten).
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```js
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const flattenDepth = (arr, depth = 1) =>
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depth != 1 ? arr.reduce((a, v) => a.concat(Array.isArray(v) ? flattenDepth (v, depth-1) : v), [])
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: arr.reduce((a,v) => a.concat(v),[]);
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// flattenDepth([1,[2],[[[3],4],5]], 2) -> [1,2,[3],4,5]
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```
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