javascript/exercises/react/example.js at docs/about · emcoding/javascript · GitHub

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class InputCell {
  constructor(value) {
    this.value = value;
    this.updated = true;
    this.subscribers = [];
  }

  setValue(value) {
    if (value !== this.value) {
      this.value = value;
      this.notify();
    }
  }

  notify() {
    this.subscribers.forEach(sub => sub.markForUpdate());
    this.subscribers.forEach(sub => sub.update());
  }

  addSubscriber(sub) {
    this.subscribers.push(sub);
  }
}


class ComputeCell {
  constructor(inputCells, fn) {
    this.fn = fn;
    this.inputCells = inputCells;
    this.inputCells.forEach(cell => cell.addSubscriber(this));
    this.subscribers = [];
    this.value = fn(inputCells);
    this.callbacks = [];
    this.updated = true;
    this.lastValue = this.value;
  }

  update() {
    const value = this.fn(this.inputCells);
    if (value !== this.value) {
      this.value = value;
      this.updated = true;
      this.notify();
    }
  }

  notify() {
    this.subscribers.forEach(sub => sub.markForUpdate());
    this.subscribers.forEach(sub => sub.update());
    this.runCallbacks();
  }

  markForUpdate() {
    this.updated = false;
    this.subscribers.forEach(sub => sub.markForUpdate());
  }

  runCallbacks() {
    if (this.allInputsUpdated() && this.valueChanged()) {
      this.lastValue = this.value;
      this.callbacks.forEach(cb => cb.run(this));
    }
  }

  allInputsUpdated() {
    return this.inputCells
      .filter(cell => cell.updated)
      .length === this.inputCells.length;
  }

  valueChanged() {
    return this.lastValue !== this.value;
  }

  addSubscriber(sub) {
    this.subscribers.push(sub);
  }

  addCallback(cb) {
    this.callbacks.push(cb);
  }

  removeCallback(cb) {
    this.callbacks = this.callbacks.filter(c => c !== cb);
  }
}


class CallbackCell {
  constructor(fn) {
    this.fn = fn;
    this.values = [];
  }

  run(cell) {
    this.values.push(this.fn(cell));
  }
}


export { InputCell, ComputeCell, CallbackCell };