Type Alias ArrGroupByCallbackFn<T>

ArrGroupByCallbackFn: (
    value: T,
    index: number,
    array: ArrayLike<T>,
) => string | number | symbol

Callback function type used by arrGroupBy to derive a group key for each element. The function is called once per element and must return a string, number, or symbol that identifies which group the element belongs to. Elements that map to the same key are collected into the same array in the result object.

Type Parameters

T
Identifies the base type of array elements

Type Declaration

- (value: T, index: number, array: ArrayLike<T>): string | number | symbol
- Parameters
  - value: T
    The current element of the array being processed.
  - index: number
    The zero-based index of the current element in the array.
  - array: ArrayLike<T>
    The array (or array-like object) that arrGroupBy was called on.
  Returns string | number | symbol
  A string, number, or symbol that identifies the group for the current element.

Since

0.14.0

Example

// Group numbers as "even" or "odd"
const parity: ArrGroupByCallbackFn<number> = (n) => n % 2 === 0 ? "even" : "odd";

arrGroupBy([1, 2, 3, 4, 5], parity);
// { odd: [1, 3, 5], even: [2, 4] }

Example

// Group objects by a property value
interface Person { name: string; dept: string; }

const byDept: ArrGroupByCallbackFn<Person> = (p) => p.dept;

const people: Person[] = [
    { name: "Alice", dept: "eng" },
    { name: "Bob",   dept: "hr"  },
    { name: "Carol", dept: "eng" }
];

arrGroupBy(people, byDept);
// {
//   eng: [{ name: "Alice", dept: "eng" }, { name: "Carol", dept: "eng" }],
//   hr:  [{ name: "Bob",   dept: "hr"  }]
// }

Example

// Use the element index to create fixed-size buckets
const bucket: ArrGroupByCallbackFn<string> = (_v, idx) => idx % 3;

arrGroupBy(["a", "b", "c", "d", "e"], bucket);
// { 0: ["a", "d"], 1: ["b", "e"], 2: ["c"] }

Type Alias ArrGroupByCallbackFn<T>

Type Parameters

Type Declaration

Parameters

Returns string | number | symbol

Since

Example

Example

Example

Settings