Reflect

Reflect.has

检查对象内有没有这个变量

  Reflect.has(Object,"assign"); //true
  "assign" in Object; //true

Reflect.get

获取对象内的指定变量

  var obj={
      name:"abc"
  }
  Reflect.get(obj,"name"); //true
  Reflect.get(obj,"age"); //false

Reflect.set

设置对象内的指定变量

  var obj={
      name:"abc"
  }
  Reflect.set(obj,"name","jpc");
  Reflect.set(obj,"age",19);
  console.log(obj) //{ name:"jpc",age:19 }

Reflect.delete

删除对象内的指定变量

  var obj={
      name:"jpc",
      area:"浙江"
  }
  Reflect.defineProperty(obj,"age",{
      value:19,
      writable:true,
      configurable:true,
      enumerable:false
  });
  Reflect.delete(obj,"name"); //true
  Reflect.delete(obj,"age"); //false
  Reflect.deltet(obj,"sex"); //true
  console.log(obj); //{ area:"浙江" }

Reflect.constructor

不使用new方法构造一个实例

  class Num{
      constructor(...args){
          for( let i of args ){
              this[i]=i;
          }
      }
      total(){
          let totalNum=0;
          for( let i in this ){ 
              totalNum+=this[i];
          };
          return totalNum;
      }
  }
  var n=Reflect.construct(Num,[5,8,9]);
  var n2=new Num(5,8,9);
  n.total()===n2.total() //true

Reflect.getPrototypeOf

获取对象的__proto__的属性 =Object.getPrototypeOf(obj)

  class Num{
      constructor(...args){
          for( let i of args ){
              this[i]=i;
          }
      }
      total(){
          let totalNum=0;
          for( let i in this ){ 
              totalNum+=this[i];
          };
          return totalNum;
      }
  }
  var n=Reflect.construct(Num,[5,8,9]);
  var n2=new Num(5,8,9);
  Reflect.getPrototypeOf(n)===Num.prototype //true
  Reflect.getPrototypeOf(n2)===Num.prototype //true

Reflect.setPrototypeOf

设置对象的__proto__属性 =Object.setPrototypeOf(obj, newProto)

  class Num{
      constructor(...args){
          for( let i of args ){
              this[i]=i;
          }
      }
      total(){
          let totalNum=0;
          for( let i in this ){ 
              totalNum+=this[i];
          };
          return totalNum;
      }
  }
  var n=Reflect.construct(Num,[5,8,9]);
  Reflect.setPrototypeOf(n,{name:"abc"});
  n.__proto__ //{ name:"abc" }

Reflect.apply

  function fun(...args){
      console.log(this); //{namespace:"fun",time:"20200709"}
      console.log(args); //[5,10]
  }
  Reflect.apply(fun,{namespace:"fun",time:"20200709"},[5,10]);
  //=Function.prototype.apply.call(fun,{namespace:"fun",time:"20200709"},[5,10])，

Reflect.defineProperty

=Object.defineProperty

Reflect.ownKeys

返回Object.getOwnPropertyNames与Object.getOwnPropertySymbols之和