尤雨溪的Vue3极简响应式代码

<script>
  let activeEffect;
  class Dep {
    constructor(value) {
      this.subscribers = new Set();
      this._value = value;
    }
    get value() {
      this.depend();
      return this._value;
    }
    set value(newValue) {
      this._value = newValue;
      this.notify();
    }
    depend() {
      if (activeEffect) {
        this.subscribers.add(activeEffect);
      }
    }
    notify() {
      this.subscribers.forEach((effect) => {
        effect();
      });
    }
  }
  function watchEffect(effect) {
    activeEffect = effect;
    effect();
    activeEffect = null;
  }
  const dep = new Dep("hello");
  watchEffect(() => {
    console.log(dep.value);
  });
  dep.value = "changed";
  dep.value = "changed2";
</script>