vue3简易实现proxy代理实例详解

const state = reactive({ name: 'cld', age: 26, like: 'paint' });
console.log("获取更改age前的值", state.age);
state.age = 28;
console.log("获取更改age后的值", state.age);

export function reactive (target) {
  // 创建一个响应式对象 对象 set map array object ...
  return createReactiveObject(target, {
    // proxy + reflect
    get (target, key, receiver) {
      // 可能无法访问key target[key]是否成功不会报错 所以使用reflect
      const res = Reflect.get(target, key, receiver); // == target[key];
      console.log('用户取值', target, key);
      return res;
    },
    set (target, key, value, receiver) {
      const res = Reflect.set(target, key, value, receiver);
      console.log('用户设置值', target, key);// == target[key]=value;
      return res;
    }
  });
}
const isObject = (obj) => { return typeof obj == 'object' && obj != null; };
function createReactiveObject (target, baseHandler) {
// 如果不是对象 不需要代理
  if (!isObject(target)) {
    return target;
  }
  // target目标对象 baseHandler get/set 值处理方法，
  const observed = new Proxy(target, baseHandler);
  return observed;
}

/** Reflect 作用
 * 可能无法访问key target[key]是否成功不会报错 
 * 所以使用reflect
 * Reflect.get 返回值   Reflect.set 返回值boolean
 **/
const res = Reflect.get(target, key, receiver);  
// Reflect.get(target, key, receiver);  等价于 target[key] 并返回值
const res = Reflect.set(target, key, value, receiver);  
// res  值为true/false 表示是否成功设置值

get (target, key, receiver) {// proxy+reflect
    const res = Reflect.get(target, key, receiver);// == target[key];
    if (isObject(res)) {
      return reactive(res);
    }
    return res;
  };

set (target, key, value, receiver) {
    const hasKey = hasOwn(target, key);
    const oldValue = target[key]; // Reflect.set 操作前还是历史数据
    const res = Reflect.set(target, key, value, receiver); 
    if (!hasKey) {
      // 新增属性
      console.log('用户新增值', target, key);
    } else if (value !== oldValue) {
      //修改操作
      console.log('用户修改值', target, key);
    }
    return res;
  };