Function indexBy

indexBy<T>(array, keyCallback): Record<string, T[]>
Creates indexed object by provided callback.

If array is returned, creates a separate index for each array element.
Type Parameters
- T
Parameters
- array: T[]
- keyCallback: ((value) => string | number | readonly (string | number)[])
  - - (value): string | number | readonly (string | number)[]
    - Parameters
      value: T
      Returns string | number | readonly (string | number)[]
Returns Record<string, T[]>
Example
```
indexBy(['one', 'two', 'three'], v => v.length)
// { '5': ['three'], '3': ['one', 'two'] }

indexBy(['one', 'two', 'three'], v => [v.length, v.length + 1])
// { '5': ['three'], '6': ['three'], '3': ['one', 'two'], '4': ['one', 'two'] }
```
- Defined in src/array.ts:381
indexBy<T>(array, keyCallback): Record<string, ReadonlyArray<T>>
Type Parameters
- T
Parameters
- array: readonly T[]
- keyCallback: ((value) => string | number | readonly (string | number)[])
  - - (value): string | number | readonly (string | number)[]
    - Parameters
      value: T
      Returns string | number | readonly (string | number)[]
Returns Record<string, ReadonlyArray<T>>
- Defined in src/array.ts:385