Proxy-Reflect详解

标签：obj name Reflect 详解 Proxy key target console log

1.监听对象属性的操作（Es5）

const obj = {
      name: "why",
      age: 18,
      height: 1.88
    }

    // 需求: 监听对象属性的所有操作
    // 监听属性的操作
    // 1.针对一个属性
    // let _name = obj.name
    // Object.defineProperty(obj, "name", {
    //   set: function(newValue) {
    //     console.log("监听: 给name设置了新的值:", newValue)
    //     _name = newValue
    //   },
    //   get: function() {
    //     console.log("监听: 获取name的值")
    //     return _name
    //   }
    // })

    // 2.监听所有的属性: 遍历所有的属性, 对每一个属性使用defineProperty
    const keys = Object.keys(obj)
    for (const key of keys) {
      let value = obj[key]
      Object.defineProperty(obj, key, {
        set: function(newValue) {
          console.log(`监听: 给${key}设置了新的值:`, newValue)
          value = newValue
        },
        get: function() {
          console.log(`监听: 获取${key}的值`)
          return value
        }
      })
    }

    // console.log(obj.name)
    // obj.name = "kobe"
    console.log(obj.age)
    obj.age = 17
    console.log(obj.age)



    // 什么是响应式?
    // const nameEl = document.querySelector(".name")
    // nameEl.textContent = obj.name
    // obj.name = "kobe"
    // obj.name = "james"

2.监听对象属性的操作（Es6）

  	const obj = {
      name: "why",
      age: 18,
      height: 1.88
    }


    // 1.创建一个Proxy对象
    const objProxy = new Proxy(obj, {
      set: function(target, key, newValue) {
        console.log(`监听: 监听${key}的设置值: `, newValue)
        target[key] = newValue
      },
      get: function(target, key) {
        console.log(`监听: 监听${key}的获取`)
        return target[key]
      }
    })

    // 2.对obj的所有操作, 应该去操作objProxy
    // console.log(objProxy.name)
    // objProxy.name = "kobe"
    // console.log(objProxy.name)
    // objProxy.name = "james"

    objProxy.address = "广州市"
    console.log(objProxy.address)

3.Proxy-其他捕获器的监听方法

	const obj = {
      name: "why",
      age: 18,
      height: 1.88
    }


    // 1.创建一个Proxy对象
    const objProxy = new Proxy(obj, {
      set: function(target, key, newValue) {
        console.log(`监听: 监听${key}的设置值: `, newValue)
        target[key] = newValue
      },
      get: function(target, key) {
        console.log(`监听: 监听${key}的获取`)
        return target[key]
      },

      deleteProperty: function(target, key) {
        console.log(`监听: 监听删除${key}属性`)
        delete obj.name
      },

      has: function(target, key) {
        console.log(`监听: 监听in判断 ${key}属性`)
        return key in target
      }
    })

    delete objProxy.name

    console.log("age" in objProxy)

4.Proxy-监听函数对象的操作

    function foo(num1, num2) {
      console.log(this, num1, num2)
    }

    const fooProxy = new Proxy(foo, {
      apply: function(target, thisArg, otherArgs) {
        console.log("监听执行了apply操作")
        target.apply(thisArg, otherArgs)
      },
      construct: function(target, otherArray) {
        console.log("监听执行了new操作")
        console.log(target, otherArray)
        return new target(...otherArray)
      }
    })

    // fooProxy.apply("abc", [111, 222])
    new fooProxy("aaa", "bbb")

5.Reflect-和Object的区别之一

    "use strict"

    const obj = {
      name: "why",
      age: 18
    }

    Object.defineProperty(obj, "name", {
      configurable: false
    })
    // Reflect.defineProperty()

    // 1.用以前的方式进行操作
    // delete obj.name
    // if (obj.name) {
    //   console.log("name没有删除成功")
    // } else {
    //   console.log("name删除成功")
    // }

    // 2.Reflect
    if (Reflect.deleteProperty(obj, "name")) {
      console.log("name删除成功")
    } else {
      console.log("name没有删除成功")
    }

6.Reflect-和Proxy共同完成代理

    const obj = {
      name: "why",
      age: 18
    }

    const objProxy = new Proxy(obj, {
      set: function(target, key, newValue, receiver) {
        // target[key] = newValue
        // 1.好处一: 代理对象的目的: 不再直接操作原对象
        // 2.好处二: Reflect.set方法有返回Boolean值, 可以判断本次操作是否成功
        const isSuccess = Reflect.set(target, key, newValue)

        if (!isSuccess) {
          throw new Error(`set ${key} failure`)
        }
      },
      get: function(target, key, receiver) {

      }
    })

    // 操作代理对象
    objProxy.name = "kobe"
    console.log(obj)

7.Reflect-Reflect设置receiver

    const obj = {
      _name: "why",
      set name(newValue) {
        console.log("this:", this) // 默认是obj
        this._name = newValue
      },
      get name() {
        return this._name
      }
    }


    // obj.name = "aaaa"

    // console.log(obj.name)
    // obj.name = "kobe"

    const objProxy = new Proxy(obj, {
      set: function(target, key, newValue, receiver) {
        // target[key] = newValue
        // 1.好处一: 代理对象的目的: 不再直接操作原对象
        // 2.好处二: Reflect.set方法有返回Boolean值, 可以判断本次操作是否成功
        /*
           3.好处三:
             > receiver就是外层Proxy对象
             > Reflect.set/get最后一个参数, 可以决定对象访问器setter/getter的this指向
        */
        console.log("proxy中设置方法被调用")
        const isSuccess = Reflect.set(target, key, newValue, receiver)

        if (!isSuccess) {
          throw new Error(`set ${key} failure`)
        }
      },
      get: function(target, key, receiver) {
        console.log("proxy中获取方法被调用")
        return Reflect.get(target, key, receiver)
      }
    })


    // 操作代理对象
    objProxy.name = "kobe"
    console.log(objProxy.name)

8.Reflect-和construct结合的反射

    function Person(name, age) {
      this.name = name
      this.age = age
    }

    function Student(name, age) {
      // Person.call(this, name, age)
      const _this = Reflect.construct(Person, [name, age], Student)
      return _this
    }

    // const stu = new Student("why", 18)
    const stu = new Student("why", 18)
    console.log(stu)
    console.log(stu.__proto__ === Student.prototype)

　　

 

标签：obj,name,Reflect,详解,Proxy,key,target,console,log
From： https://www.cnblogs.com/yoyo1216/p/17048614.html