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30-seconds-of-code/snippets/mapKeys.md
2018-01-11 20:33:14 +02:00

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### mapKeys
Creates an object with keys generated by running the provided function for each key and the same values as the provided object.
Use `Object.keys(obj)` to iterate over the object's keys.
Use `Array.reduce()` to create a new object with the same values and mapped keys using `fn`.
```js
const mapKeys = (obj, fn) =>
Object.keys(obj).reduce((acc,k) => {acc[fn(obj[k], k, obj)] = obj[k]; return acc;},{});
```
```js
mapKeys({ 'a': 1, 'b': 2 }, (val, key) => key + val); // { a1: 1, b2: 2 }
```