Function groupData

src/util/model.ts:1057–1078

(
    array: T[],
    getKey: (item: T) => R // return key
)

 * Group a list by key.
 */
export function groupData<T, R extends string | number>(
    array: T[],
    getKey: (item: T) => R // return key
): {
    keys: R[],
    buckets: HashMap<T[], R> // hasmap key: the key returned by `getKey`.
} {
    const buckets = createHashMap<T[], R>();
    const keys: R[] = [];

    each(array, function (item) {
        const key = getKey(item);
        (buckets.get(key)
            || (keys.push(key), buckets.set(key, []))
        ).push(item);
    });

    return {
        keys: keys,
        buckets: buckets
    };
}


/**