export declare type GroupedElements<GroupIdType extends number | string, ElementType> = {
    [groupId in GroupIdType]: ElementType[];
};
/**
 * Creates an object where the key is the group id and the value is an array of elements grouped by this id.
 *
 * @param array - The array to group elements from
 * @param mapper - The function that returns the group id
 * @returns An object where the key is the group id and the value is an array of elements grouped by this id
 *
 * @public
 */
export default function group<ElementType, GroupIdType extends string | number>(arr: ElementType[], mapper: (element: ElementType, index: number) => GroupIdType): GroupedElements<GroupIdType, ElementType>;
/**
 * Creates an object where the key is the group id and the value is an array of elements grouped by this id.
 *
 * @param array - The array to group elements from
 * @param key - The name of the field to use as the id
 * @returns An object where the key is the group id and the value is an array of elements grouped by this id
 *
 * @public
 */
export default function group<ElementType extends {}, Key extends keyof ElementType, GroupIdType extends ElementType[Key]>(arr: ElementType[], key: Key): GroupIdType extends number | string ? GroupedElements<GroupIdType, ElementType> : never;