18 lines
608 B
Markdown
18 lines
608 B
Markdown
### groupBy
|
|
|
|
Groups the elements of an array based on the given function.
|
|
|
|
Use `Array.map()` to map the values of an array to a function or property name.
|
|
Use `Array.reduce()` to create an object, where the keys are produced from the mapped results.
|
|
|
|
```js
|
|
const groupBy = (arr, func) =>
|
|
arr.map(typeof func === 'function' ? func : val => val[func])
|
|
.reduce((acc, val, i) => { acc[val] = (acc[val] || []).concat(arr[i]); return acc; }, {});
|
|
```
|
|
|
|
```js
|
|
groupBy([6.1, 4.2, 6.3], Math.floor) // {4: [4.2], 6: [6.1, 6.3]}
|
|
groupBy(['one', 'two', 'three'], 'length') // {3: ['one', 'two'], 5: ['three']}
|
|
```
|