groupBy
The groupBy function groups the elements of an array according to the value returned by a key selector function.
Syntax
typescript
groupBy<T, K extends PropertyKey>(
array: T[],
keySelector: (value: T, index: number) => K
): Record<K, T[]>;Parameters
| Name | Type | Description |
|---|---|---|
array | T[] | Source array |
fn | (value: T, index: number, array: T[]) => K | Grouping function |
Returns
| Type | Description |
|---|---|
Record<K, T[]> | Object with grouped arrays |
Examples
typescript
groupBy([1, 2, 3, 4], x => x % 2); // => {0: [2,4], 1: [1,3]}
groupBy(["a", "b", "aa"], x => x.length); // => {1: ["a","b"], 2: ["aa"]}Notes
- Useful for categorizing elements by custom criteria.