Reflect、promise

一、Reflect映射
defineProperty() 参数：obj：具体的对象、attr：属性、{value}：属性值

var obj = {};
Object.defineProperty(obj, 'age', {
  value:18
});
Reflect.defineProperty(obj, 'name', {
  value:"张三"
});

console.log('name' in obj)
//映射进行判断属性
console.log(Reflect.has(obj, 'age'))

let obj = {
  age:18
}
//proxy 阻截
new Proxy(obj, {
  set:function(){

  }
});
//Reflect.set(target, attr, value, self)
Reflect.set(obj, 'name', '张三')

let proxy = new Proxy(obj, {
  set:function(target, attr, value, self){
    Reflect.set(target, attr, value, self)
  }
});

二、Reflect静态方法

var obj = {
  age:18,
  set index(val){
    this.age = val;  //this指向obj1
  }
}
var obj1 = {
  age:20
}
var r = Reflect.get(obj, 'age')
console.log(r)
Reflect.set(obj, 'index', 30, obj1)
console.log(obj1, obj)

var obj = {
  age:18,
  [Symbol()]:999
}
var obj1 = {
  index:888
}
console.log(obj)
//deleteProperty  删除属性
Reflect.deleteProperty(obj, 'age')
//Reflect.setPrototypeOf(obj, obj1)  设置修改原型
console.log(obj, obj1)
/*
writable：可写的
  样式可读：obj.age
enumerable：可列举的（可遍历的，可枚举）
  for(), for...in, for...of
configurable
  样式可写：obj.age = 99;
*/
var r = Reflect.getOwnPropertyDescriptor(obj, 'age');
console.log(r)
Reflect.defineProperty(
  obj, 'index', {
    value:999
  }
);
console.log(obj)
for(var key in obj){
  console.log(key)
}
//Reflect.ownKeys(obj)  //遍历所有的属性，包括私有的属性
for(var key of Reflect.ownKeys(obj)){
  console.log(key)
}

function Fn(x, y){
  this.x = x;
  this.y = y;
}
var obj = new Fn(10, 20)
console.log(obj)

var obj1 = Reflect.construct(Fn, [30, 40])
console.log(obj1)

//Reflect.isExtensible(target)  判断扩展
//Reflect.preventExtensions  阻止扩展
var obj = {
  age:18
}
var r = Reflect.isExtensible(obj);
console.log(r)
obj.index = 666;
console.log(obj)
r = Reflect.preventExtensions(obj)
obj.name = "张三";
console.log(obj)

三、Promise
状态：pending 进行中、resolved 已解决（fulfilled 已成功、rejected 已失败）

var promise = new Promise(
  function(success, error){
    success("成功");
  }
);
console.log(promise)
var promise1 = new Promise(
  function(success, error){
    error("失败了！");
  }
  //(success, error) => {
  //  error("失败了！");
  //}
)
console.log(promise1);

var promise = new Promise(
  //形参：第一个值：诺言成功；第二个值：诺言失败
  function(success, error){
    setTimeout(()=>{
      error()
    }, 3000);
  }
);
console.log(promise)
promise.then(function(){
  console.log("成功了！");
}, function(){
  console.log("失败了！");
})

var promise = new Promise(function(success, error){
  setTimeout(()=>{
    success("已经成功了！");
    //error("已经失败了");
  }, 3000);
});
promise.then((message)=>{
  console.log(message)
}, (message)=>{
  console.log(message)
});

catch 捕获到错误的信息

promise.then(function(){
  console.log("ok");
}).catch(function(){
  console.log("error")
});
var promise = new Promise(function(success, error){
  //  catch 对throw newError的内容进行捕获
  throw new Error("Uncaught SyntaxError: missing  after argument list");
});
promise.then(function(){
  console.log("ok")
}).catch(function(e){
  console.log(e)
});

PromiseStatus 已经完成了
PromiseValue 已经完成时反馈出来的值

var promise = Promise.resolve("404");
console.log(promise)

var promise1 = new Promise((success, error) => {
  success("404");
})
console.log(promise1)

var p1 = new Promise((success, error) => {
  success();
})
var p2 = new Promise((success, error) => {
  success();
})
var p3 = new Promise((success, error) => {
  success();
})
var promise = Promise.all([p1, p2, p3]);
promise.then(()=>{
  console.log("诺言全成功")
}, ()=>{
  console.log("诺言有一个失败")
})

var p1 = new Promise((success, error) => {
  setTimeout(()=>{
    error("已经失败了");
  }, 3000)
})
var p2 = new Promise((success, error) => {
  setTimeout(()=>{
    error("已经失败了");
  }, 2000)
})
var p3 = new Promise((success, error) => {
  setTimeout(()=>{
    success("已经成功了");
  }, 1000)
})
var promise = Promise.race([p1, p2, p3]);
promise.then(()=>{
  console.log("诺言第一个成功")
}, ()=>{
  console.log("诺言第一个失败")
})