1. //用Proxy实现数据响应式（vue3.0）,粘贴的
    3. let onWatch = (obj, setBind, getLogger) => {
    4.   let handler = {
    5.    get(target, property, receiver) {
    6.      getLogger(target, property)
    7.      // 这句判断代码是新增的,这里体现了Proxy不用一层层递归去为每个属性添加代理，性能上更优
    8.      //vue3.0中使用了Proxy替代了原来的Object.defineProperty
    9.      if (typeof target[property] === 'object' && target[property] !== null) {
    10.        return new Proxy(target[property], handler);
    11.      } else {
    12.        return Reflect.get(target, property);
    13.      }
    14.     },
    15.     set(target, property, value, receiver) {
    16.       setBind(value, property)
    17.       return Reflect.set(target, property, value)
    18.     }
    19.   }
    20.   return new Proxy(obj, handler)
    21. }
    23. let obj = { a: 1 }
    24. let p = onWatch(
    25.   obj,
    26.   (v, property) => {
    27.     console.log(`监听到属性${property}改变为${v}`)
    28.   },
    29.   (target, property) => {
    30.     console.log(`'${property}' = ${target[property]}`)
    31.   }
    32. )
    33. p.a = 2 // 监听到属性a改变
    34. p.a // 'a' = 2