class Pipeline {
  #value;
  #steps = [];

  constructor(value) {
    this.#value = value;
  }

  map(fn) {
    this.#steps.push({ type: 'map', fn });
    return this;
  }

  filter(fn) {
    this.#steps.push({ type: 'filter', fn });
    return this;
  }

  execute() {
    return this.#steps.reduce((acc, step) => {
      if (step.type === 'map') return acc.map(step.fn);
      if (step.type === 'filter') return acc.filter(step.fn);
      return acc;
    }, this.#value);
  }
}

const result = new Pipeline([1, 2, 3, 4, 5, 6])
  .filter(x => x % 2 === 0)
  .map(x => x ** 2)
  .filter(x => x > 10)
  .map(x => x - 1)
  .execute();

console.log(result);