// vue 2.5.0
var arrayProto = Array.prototype;
var arrayMethods = Object.create(arrayProto); // Array {}
function def(obj, key, val, enumerable) {
  Object.defineProperty(obj, key, {
   value: val,
   enumerable: !!enumerable,
   writable: true,
   configurable: true
  });
}
var methodsToPatch = [
  'push',
  'pop',
  'shift',
  'unshift',
  'splice',
  'sort',
  'reverse'
  ];

  /**
  * Intercept mutating methods and emit events
  */
  methodsToPatch.forEach(function(method) {
  // cache original method
  var original = arrayProto[method]; 
    // 比如 method是push，则结果为
    // "htmlcode">

  let proxy = new Proxy(fruit, {
    get: function (obj, prop) {
      return prop in obj "newVal", newVal) // 输出{ name: "lemon", num: 999 }
      return true;
    }
  })
  proxy.push({ name: "lemon", num: 999 })
  console.log(fruit)





Proxy代理可以劫持对象的改变，defineProperty需要遍历


defineProperty




   let fruit = {
     "apple": 2,
     "pear": 22,
     "peach": 222
  }
  Object.keys(fruit).forEach(function (key) {
      Object.defineProperty(fruit[i], key, {
        enumerable: true,
        configurable: true,
        get: function () {
          return val;

        },
        set: function (newVal) {
          val = newVal; // 输出 newVal 888
          console.log("newVal", newVal)
        }
      })
    })
   fruit.apple = 888




Proxy




   let fruit = {
     "apple": 2,
     "pear": 22,
     "peach": 222
  }
  let proxy = new Proxy(fruit, {
    get: function (obj, prop) {
      return prop in obj "newVal", newVal) // 输出 newVal 888
      return true;
    }
  })
  proxy.apple = 888




Proxy代理可以劫持对象属性的添加，defineProperty用this.$set来实现

defineProperty，如果属性不存在，则需要借助this.$set




<div id="app">
  <span v-for="(value,name) in fruit">{{name}}:{{value}}个 </span> 
  <button @click="add()">添加柠檬</button>
</div>
<script src="/UploadFiles/2021-04-02/vue">



  Object.keys(fruit).forEach(function (key) {
    Object.defineProperty(fruit, key, {
      enumerable: true,
      configurable: true,
      get: function () {
        return val;

      },
      set: function (newVal) {
        val = newVal;
        console.log("newVal", newVal) // 根本没有进去这里
      }
    })
  })




Proxy 直接可以添加属性




// vue 3
<div id="app">
  <span v-for="(value,name) in fruit">{{name}}:{{value}}个 </span>
  <button @click="add()">添加柠檬</button>
</div>
<script src="/UploadFiles/2021-04-02/vue@next">



  let proxy = new Proxy(fruit, {
    get: function (obj, prop) {
      return prop in obj "newVal", newVal) // lemon, 888
      return true;
    }
  })
  proxy.lemon = 888




Proxy


其他属性

应用场景 promisify化


用Proxy写一个场景，请求都是通过回调，如果我们需要用promise包一层的话，则可以




// server.js
// 假设这里都是回调
export const searchResultList = function (data, callback, errorCallback) {
 axios.post(url, data, callback, errorCallback)
}





// promisify.js
import * as server from './server.js'
const promisify = (name,obj) => (option) => {
 return new Promise((resolve, reject) => {
  return obj[name](
   option,
   resolve,
   reject,
  )
 })
}
const serverPromisify = new Proxy(server, {
 get (target,prop) {
  return promisify(prop, server)
 }
})
export default serverPromisify




使用




// index.js
import serverPromisify from './serverPromisify'
serverPromisify.searchResultList(data).then(res=>{

})




如有不正确，望请指出

留下一个疑问，既然兼容性不是很好，那么尤大是怎么处理polyfill呢
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