38 lines
1.2 KiB
Markdown
38 lines
1.2 KiB
Markdown
---
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title: Unflatten object
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tags: object
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cover: purple-flower-bunch
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firstSeen: 2018-02-07T11:30:18+02:00
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lastUpdated: 2020-10-22T20:24:44+03:00
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---
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Unflatten an object with the paths for keys.
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- Use nested `Array.prototype.reduce()` to convert the flat path to a leaf node.
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- Use `String.prototype.split()` to split each key with a dot delimiter and `Array.prototype.reduce()` to add objects against the keys.
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- If the current accumulator already contains a value against a particular key, return its value as the next accumulator.
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- Otherwise, add the appropriate key-value pair to the accumulator object and return the value as the accumulator.
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```js
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const unflattenObject = obj =>
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Object.keys(obj).reduce((res, k) => {
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k.split('.').reduce(
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(acc, e, i, keys) =>
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acc[e] ||
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(acc[e] = isNaN(Number(keys[i + 1]))
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? keys.length - 1 === i
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? obj[k]
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: {}
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: []),
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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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unflattenObject({ 'a.b.c': 1, d: 1 }); // { a: { b: { c: 1 } }, d: 1 }
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unflattenObject({ 'a.b': 1, 'a.c': 2, d: 3 }); // { a: { b: 1, c: 2 }, d: 3 }
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unflattenObject({ 'a.b.0': 8, d: 3 }); // { a: { b: [ 8 ] }, d: 3 }
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```
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