vue3 reactive响应式依赖收集派发更新原理是什么

function reactive(raw) {
  return new Proxy(raw, {
    get(target, key) {
      const res = Reflect.get(target, key);
      //添加依赖
      track(target, key as string);
      return res;
    },
    set(target, key, value) {
      const res = Reflect.set(target, key, value);
      trigger(target, key);
      return res;
    },
  });
}

const targetMap = new WeakMap();
function track(target, key) {
  let depsMap = targetMap.get(target);
  if (!depsMap) {
    depsMap = new Map();
    targetMap.set(target, depsMap);
  }
  let dep = depsMap.get(key);
  if (!dep) {
    dep = new Set();
    depsMap.set(key, dep);
  }
  dep.add(currentEffect);
}

class ReactiveEffect {
  private fn: Function;
  constructor(_fn: Function) {
    this.fn = _fn;
  }
  run() {
    currentEffect = this;
    this.fn();
  }
}
let currentEffect: null | ReactiveEffect = null;
function effect(fn: Function) {
  const reactiveEffect = new ReactiveEffect(fn);
  reactiveEffect.run();
}

function trigger(target, key) {
  let depsMap = targetMap.get(target);
  let dep = depsMap.get(key);
  for (let effect of dep) {
    effect.fn();
  }
}