SOURCE

let subscribe = (obj,observable) => {
  let handler = {
    get(target, property, receiver) {
       console.log(`'${property}' 的值为 ${target[property]}`)
       observable(arguments)
      return Reflect.get(target, property, receiver)
    },
    set(target, property, value, receiver) {
       console.log(`监听到属性${property}改变为${value}`)
       observable(arguments)
      return Reflect.set(target, property, value)
    }
  }
  return new Proxy(obj, handler)
}

let obj = { a: 1 }
let p = subscribe(obj,(args)=>{
    console.log(args)
})
p.a = 2 // 监听到属性a改变
p.a // 'a' = 2