Angular GetterMemo, to prevent recalculations based on a list of values

getter-memo.ts

export default class GetterMemo<V, C extends any[] = any[]> {
  constructor(
    private _calculator: () => V,
    private _valueSeparators: () => C
  ) {}

  private _lastValue?: V;
  private _lastUpdate?: C;

  clear() {
    this._lastValue = undefined;
    this._lastUpdate = undefined;
  }

  reload() {
    this.clear();
    return this.getValue();
  }

  check(current = this._valueSeparators()) {
    const lastUpdate = this._lastUpdate;
    if (lastUpdate) {
      if (current.every((_, i) => current[i] === lastUpdate[i])) {
        return false;
      }
    }
    return true;
  }

  getValue() {
    const current = this._valueSeparators();
    if (this.check(current)) {
      this._lastValue = this._calculator();
      this._lastUpdate = current;
    }
    return this._lastValue as V;
  }
}

/**
How to use

public input = "1,2,3,4,5,6,7,8,9"
private _oddNumbers = new GetterCache(
  // First Parameter: the calculation function, will be disponible in GetterCache.getValue
  () => input.split(",").map(n => parseInt(n, 10)).filter(n => !isNaN(n) && n % 2 == 1),
  // Second Parameter: A list of values to === compare with the last list
  () => [this.input]
);
get odd() {
  return this._oddNumbers.getValue();
}
*/