Method transform

packages/common/src/pipes/keyvalue_pipe.ts:118–147

(
    input: undefined | null | {[key: string]: V; [key: number]: V} | ReadonlyMap<K, V>,
    compareFn: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null = defaultComparator,
  )

  ): T extends object ? Array<KeyValue<keyof T, T[keyof T]>> : null;

  transform<K, V>(
    input: undefined | null | {[key: string]: V; [key: number]: V} | ReadonlyMap<K, V>,
    compareFn: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null = defaultComparator,
  ): Array<KeyValue<K, V>> | null {
    ngDevMode && warnIfSignal('KeyValuePipe', input);

    if (!input || (!(input instanceof Map) && typeof input !== 'object')) {
      return null;
    }

    // make a differ for whatever type we've been passed in
    this.differ ??= this.differs.find(input).create();

    const differChanges: KeyValueChanges<K, V> | null = this.differ.diff(input as any);
    const compareFnChanged = compareFn !== this.compareFn;

    if (differChanges) {
      this.keyValues = [];
      differChanges.forEachItem((r: KeyValueChangeRecord<K, V>) => {
        this.keyValues.push(makeKeyValuePair(r.key, r.currentValue!));
      });
    }
    if (differChanges || compareFnChanged) {
      if (compareFn) {
        this.keyValues.sort(compareFn);
      }
      this.compareFn = compareFn;
    }
    return this.keyValues;
  }
}

export function defaultComparator<K, V>(