Object.getOwnPropertyDescriptor()

语法

getOwnPropertyDescriptor(o: any, p: PropertyKey): PropertyDescriptor | undefined;

描述

返回指定对象上一个自有属性对应的属性描述符。自有属性指的是直接赋予该对象的属性，因此原型链上的属性会返回 undefined.

示例

const obj = {
  firstName: "Yancey",
  lastName: "Leo",
  greeting() {
    return `Hello, ${this.firstName}!`;
  }
};

Object.defineProperties(obj, {
  age: {
    value: 18,
    enumerable: true
  },
  lastName: {
    get() {
      return "Yancey";
    }
  }
});

Object.getOwnPropertyDescriptor(obj, "firstName");
// 输出： {value: 'Yancey', writable: true, enumerable: true, configurable: true}

Object.getOwnPropertyDescriptor(obj, "lastName");
// 输出：{get: [Function: get], set: undefined, enumerable: true, configurable: true}

Object.getOwnPropertyDescriptor(obj, "age");
// 输出：{value: 18, writable: false, enumerable: true, configurable: false}

而对于原型链上的属性，该方法直接返回 undefined

function Dog(name, color) {
  this.name = name;
  this.color = color;
}

Dog.prototype.bark = function() {
  return "汪汪~";
};

const husky = new Dog("旺财", "pink");

Object.getOwnPropertyDescriptor(Dog, "bark"); // false

Object.getOwnPropertyDescriptor(Dog, "name");
// 输出：{value: 'Dog', writable: false, enumerable: false, configurable: true}

Object.getOwnPropertyDescriptor(husky, "name");
// 输出：{value: '旺财', writable: true, enumerable: true, configurable: true}