34 lines
1.1 KiB
Markdown
34 lines
1.1 KiB
Markdown
---
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title: flattenObject
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tags: object,recursion,advanced
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firstSeen: 2018-02-07T11:30:18+02:00
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lastUpdated: 2020-10-19T18:51:03+03:00
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---
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Flattens an object with the paths for keys.
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- Use recursion.
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- Use `Object.keys(obj)` combined with `Array.prototype.reduce()` to convert every leaf node to a flattened path node.
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- If the value of a key is an object, the function calls itself with the appropriate `prefix` to create the path using `Object.assign()`.
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- Otherwise, it adds the appropriate prefixed key-value pair to the accumulator object.
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- You should always omit the second argument, `prefix`, unless you want every key to have a prefix.
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```js
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const flattenObject = (obj, prefix = '') =>
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Object.keys(obj).reduce((acc, k) => {
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const pre = prefix.length ? `${prefix}.` : '';
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if (
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typeof obj[k] === 'object' &&
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obj[k] !== null &&
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Object.keys(obj[k]).length > 0
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)
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Object.assign(acc, flattenObject(obj[k], pre + k));
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else acc[pre + k] = obj[k];
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return acc;
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}, {});
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```
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```js
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flattenObject({ a: { b: { c: 1 } }, d: 1 }); // { 'a.b.c': 1, d: 1 }
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```
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