Function groupBy

groupBy<T, G>(array: T[], keyCallback: (value: T) => G): [G, T[]][]
Groups an array's items into [key, values] entries, keyed by the callback's return value.

Internally backed by a Map keyed on the raw callback value, so:
- Object/array keys use identity (two equal-but-different object instances are distinct groups). For value equality, return a primitive key.
- Functions, symbols, and circular references work (no JSON.stringify).
- Entries are returned in first-seen order.
Type Parameters
- T
- G
Parameters
- array: T[]
- keyCallback: (value: T) => G
Returns [G, T[]][]
Example
```
groupBy([6.1, 4.2, 6.3], Math.floor)
// [ [6, [6.1, 6.3]], [4, [4.2]] ]
```
- Defined in src/array.ts:297
groupBy<T, G>(
array: readonly T[],
keyCallback: (value: T) => G,
): readonly [G, readonly T[]][]
Groups an array's items into [key, values] entries, keyed by the callback's return value.

Internally backed by a Map keyed on the raw callback value, so:
- Object/array keys use identity (two equal-but-different object instances are distinct groups). For value equality, return a primitive key.
- Functions, symbols, and circular references work (no JSON.stringify).
- Entries are returned in first-seen order.
Type Parameters
- T
- G
Parameters
- array: readonly T[]
- keyCallback: (value: T) => G
Returns readonly [G, readonly T[]][]
Example
```
groupBy([6.1, 4.2, 6.3], Math.floor)
// [ [6, [6.1, 6.3]], [4, [4.2]] ]
```
- Defined in src/array.ts:301