1.   function reactive(obj) {
    2.     const handler = {
    3.       get(target, prop, receiver) {
    4.         track(target, prop)
    5.         const value = Reflect.get(...arguments)
    6.         if (typeof value === 'object') {
    7.           return reactive(value)
    8.         } else {
    9.           return value
    10.         }
    11.       },
    12.       set(target, key, value, receiver) {
    13.         trigger(target, key, value)
    14.         return Reflect.set(...arguments)
    15.       }
    16.     }
    17.     return new Proxy(obj, handler)
    18.   }
    19.   function track(data, key) {
    20.     console.log('get data ', key)
    21.   }
    23.   function trigger(data, key, value) {
    24.     console.log('set data', key, ":", value)
    25.   }
    28.   const dinner = {
    29.     meal: 'tacos'
    30.   }
    31.   const proxy = reactive(dinner)
    32.   proxy.meal = 'apple'
    33.   proxy.list = []
    34.   proxy.list.push(1) //响应式