Function groupBy

groupBy<T, K extends PropertyKey>(
array: readonly T[],
iteratee: (item: T) => K,
): Record<K, T[]>
Groups the elements of an array based on the given function.

This function takes an array and a grouping function, and returns an object where each key is a value returned by the grouping function, and the value is an array of elements that produced that key.

根据给定函数对数组元素进行分组。

此函数接收一个数组和一个分组函数，返回一个对象，其中每个键是由分组函数返回的值，值是产生该键的元素数组。
Type Parameters
- T
- K extends PropertyKey
Parameters
- array: readonly T[]
  The array to group. 要分组的数组
- iteratee: (item: T) => K
  The function to transform elements into group keys. 将元素转换为分组键的函数
Returns Record<K, T[]>
An object with grouped elements. 分组后的对象
Remarks
Uses Map for O(1) key lookup, overall O(n) time complexity

使用 Map 实现 O(1) 键查找，整体时间复杂度 O(n)
Example
```
groupBy([{ type: 'a', val: 1 }, { type: 'b', val: 2 }, { type: 'a', val: 3 }], x => x.type)
// => { a: [{ type: 'a', val: 1 }, { type: 'a', val: 3 }], b: [{ type: 'b', val: 2 }] }
```
Example
```
groupBy([6.1, 4.2, 6.3], Math.floor)
// => { 6: [6.1, 6.3], 4: [4.2] }
```
Example
```
groupBy(['one', 'two', 'three'], x => x.length)
// => { 3: ['one', 'two'], 5: ['three'] }
```
- Defined in src/array/group-by.ts:42