为什么 Object.getOwnPropertyNames() 不起作用

Question

在这里找到答案：Javascript what is property in hasOwnProperty?

在这篇文章中如何显示一个对象的所有方法？，它说“您可以使用 Object.getOwnPropertyNames() 来获取属于一个对象的所有属性，无论是否可枚举”。通过示例，我们可以看到所有属性都包括Math列出的对象的方法。我尝试并得到了相同的结果。

然后我尝试定义我自己的对象并以相同的方式列出它的属性，但为什么没有列出方法？例如console.log(Object.getOwnPropertyNames(animal))为什么它只返回["name", "weight"]而不包括"eat", "sleep" and wakeUp？

function Animal(name, weight) {
    this.name = name;
    this.weight = weight;
}

Animal.prototype.eat = function() {
    return `${this.name} is eating!`;
}

Animal.prototype.sleep = function() {
    return `${this.name} is going to sleep!`;
}

Animal.prototype.wakeUp = function() {
    return `${this.name} is waking up!`;
}

var animal = new Animal('Kitten', '5Kg');
console.log(Object.getOwnPropertyNames(animal));  // ["name", "weight"]

另一个例子是，为什么下面的一个返回属于超类的属性，因为它是Triangle从Shape. 因为console.log(Object.getOwnPropertyNames(triangle));我们假设只有["a", "b", "c"]没有"type"？

class Shape {
  constructor(type) {
    this.type = type;
  }
  getType() {
    return this.type;
  }
}

class Triangle extends Shape {
  constructor(a, b, c) {
    super("triangle");
    this.a = a;
    this.b = b;
    this.c = c;
  }
  getParamiter() {
    return this.a + this.b + this.c;
  }
}

const triangle = new Triangle(1,2,3);
console.log(Object.getOwnPropertyNames(triangle));   //["type", "a", "b", "c"]

Answer 1

所有名称中带有“own”的对象方法只查看对象中直接存在的属性，而不是从原型继承的属性。

您可以使用Object.getPrototypeOf()获取原型，然后调用Object.getOwnProperties()它。

那只会得到直接原型的方法。如果您想要整个链，则需要编写一个循环，该循环会一直调用getPrototypeOf()直到到达Object.

function Animal(name, weight) {
    this.name = name;
    this.weight = weight;
}

Animal.prototype.eat = function() {
    return `${this.name} is eating!`;
}

Animal.prototype.sleep = function() {
    return `${this.name} is going to sleep!`;
}

Animal.prototype.wakeUp = function() {
    return `${this.name} is waking up!`;
}


function Gorilla(name, weight) {
    Animal.call(this, name, weight);
}

Gorilla.prototype = Object.create(Animal.prototype);
Gorilla.prototype.constructor = Gorilla;

Gorilla.prototype.climbTrees = function () {
    return `${this.name} is climbing trees!`;
}

Gorilla.prototype.poundChest = function() {
    return `${this.name} is pounding its chest!`;
}

Gorilla.prototype.showVigour = function () {
    return `${Animal.prototype.eat.call(this)} ${this.poundChest()}`;
}

Gorilla.prototype.dailyRoutine = function() {
    return `${Animal.prototype.wakeUp.call(this)} ${this.poundChest()} ${Animal.prototype.eat.call(this)} ${Animal.prototype.sleep.call(this)}`;
}

var animal = new Animal('Kitten', '5Kg');
console.log(Object.getOwnPropertyNames(animal));  // ["name", "weight"]
console.log(Object.getOwnPropertyNames(Object.getPrototypeOf(animal)));
var gorilla = new Gorilla('George', '160Kg');
console.log(Object.getOwnPropertyNames(gorilla)); console.log(Object.getOwnPropertyNames(Object.getPrototypeOf(gorilla)));