详解js创建对象的几种方式和对象方法

 function getObj(name, age) {
  let obj = {}
  obj.name = name
  obj.age = age
  return obj
 }
 let person1 = getObj("cc", 31)

 function CreateObj(name, age) {
  this.name = name
  this.age = age
 }
 let person1 = new CreateObj("cc", 31)
 console.log(person1)
 console.log(person1.constructor === CreateObj); // true
 console.log(person1 instanceof CreateObj); // true

 function CreateObj(name, age) {
  this.name = name
  this.age = age
 }
 CreateObj('cc', 10)
 console.log(window.name) // 'cc'

person1.sayName( ) === person2.sayName( ) // false

 function sayName() {
  console.log(this.name)
 }
 function CreatePerson(name, age) {
  this.name = name
  this.age = age
  this.sayName = sayName
 }
 let person1 = new CreatePerson('joy', 31)
 person1.sayName()

 function Person() { }
 let person1 = new Person()
 console.log(person1.__proto__ === Person.prototype)  // true
 console.log(Person.prototype.constructor === Person); // true

// isPrototypeOf判断构造函数的原型对象是否是实例的原型对象
function Person() {}
 let person1 = new Person()
 console.log(Person.prototype.isPrototypeOf(person1)); // true

// 获取对象的原型对象
 function Person() {}
 let person1 = new Person()
 console.log(Object.getPrototypeOf(person1) === Person.prototype);

// 将某个对象，设为另一个对象的原型对象
 let person1 = {name: "cc"}
 let person2 = {age: 32}
 Object.setPrototypeOf(person1,person2)
 console.log(person1.name, person1.age); // cc 32

// 以某个对象为原型对象，创建一个新对象  
let person1 = {name: "cc"}
 let person2 = Object.create(person1)
 person2.age = 30
 console.log(person2.name, person2.age);

 function Person() {}
 Person.prototype.name = "cc"
 let person1 = new Person()
 console.log(person1.name) // 'cc'
 console.log(person1.hasOwnProperty("name")); // false

// 对象自身 or 原型上找到，都返回true 
function Person() {}
 Person.prototype.name = "cc"
 let person1 = new Person()
 console.log("name" in person1) // true
 console.log(person1.hasOwnProperty("name")); // false

Object.keys( )
for ... in // 继承属性也会遍历出来
Object.getOwnPropertyNames(obj) // 会列出可枚举和不可枚举属性，其他和 Object.keys( )结果一样
Object.getOwnPropertySymbols(obj) // 和getOwnPropertyNames类似，只是仅针对symbol
Reflect.ownKeys(obj) // 和Object.keys( )结果一样

 function Person() {}
 Person.prototype.name = "cc"
 let person = new Person()
 person.age = 21
 let sy = Symbol('sy')
 person[sy] = 'smile'
 console.log(Object.values(person)) // [ 21 ]
 console.log(Object.entries(person)) // [ [ 'age', 21 ] ]