declare interface Map<K, V> {
  getOrCreate(key: K, newValue: V): V;

  getOrCreate(key: K, newValueFn: () => V): V;

  update(key: K, updateFn: (v: V | undefined) => V): void;
}

Map.prototype.getOrCreate = function <K, V>(this: Map<K, V>, key: K, newValue: V | (() => V)): V {
  if (!this.has(key)) {
    if (newValue instanceof Function) {
      this.set(key, newValue());
    } else {
      this.set(key, newValue);
    }
  }

  return this.get(key)!;
};

Map.prototype.update = function <K, V>(
  this: Map<K, V>,
  key: K,
  updateFn: (v: V | undefined) => V,
): void {
  const val = this.get(key);
  const res = updateFn(val);
  this.set(key, res);
};