All files / array/operator groupBy.ts

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
 
 
3x
 
6x
6x
4x
4x
4x
3x
3x
 
4x
 
2x
 
 
 
 
import {Dictionary, KeyProjection} from 'fnxt/fnxt-types';
 
export const groupBy = <E>(mapping: KeyProjection<E>) => (array: E[]): E[][] => {
 
  const map: Dictionary<E[]> = {};
  for (const element of array) {
    const key = mapping(element);
    let list = map[key];
    if (!list) {
      list = [];
      map[key] = list;
    }
    list.push(element);
  }
  return Object.values(map);
 
};