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30-seconds-of-code/snippets/flattenObject.md
30secondsofcode 12238b8e78 Travis build: 1581
2018-02-07 09:31:31 +00:00

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### flattenObject
Flatten an object with the paths for keys.
Use recursion.
Use `Object.keys(obj)` combined with `Array.reduce()` to convert every leaf node to a flattened path node.
If the value of a key is an object, the function calls itself with the appropriate `prefix` to create the path using `Object.assign()`.
Otherwise, it adds the appropriate prefixed key-value pair to the accumulator object.
You should always omit the second argument, `prefix`, unless you want every key to have a prefix.
```js
const flattenObject = (obj, prefix = '') =>
Object.keys(obj).reduce((acc, k) => {
const pre = prefix.length ? prefix + '.' : '';
if (typeof obj[k] === 'object') Object.assign(acc, flattenObject(obj[k], pre + k));
else acc[pre + k] = obj[k];
return acc;
}, {});
```
```js
flattenObject({ a: { b: { c: 1 } }, d: 1 }); // { 'a.b.c': 1, d: 1 }
```