Object 对象

• Object.getPrototypeOf
• Object.getOwnPropertyDescriptor
• Object.getOwnPropertyNames
• Object.create
• Object.defineProperty
• Object.defineProperties
• Object.seal
• Object.freeze
• Object.preventExtensions
• Object.isSealed
• Object.isFrozen
• Object.isExtensible
• Object.keys

Object.defineProperty()

直接在一个对象上定义一个新属性，或修改一个对象的现有属性，并返回此对象

语法

Object.defineProperty(obj, prop, descriptor)

• obj 要定义属性的对象
• prop 要定义或修改的属性名称或Symbol
• desciptor 要定义或修改的属性描述符
  • value 值
  • writable 对象的这个值是否可改 bool
  • enumerable 对象的这个值是否可枚举 bool for in
  • configurable 对象的这个值的配置是否可改 bool

const object1 = {};
Object.defineProperty(object1, "property1", {
  value: 42,
  writable: false,
});
Object1.property = 77; // throws an error in strict mode
console.log(object1.property1); // 42

Object.keys()

var json = {
  a: 1,
  b: 2,
};
console.log(Object.keys(json));
console.log(Object.values(json));

Object.create()

创建一个拥有指定原型和若干个指定属性的对象 Object.create(proto, [, propertiesObject])

var json = {
  a: 1,
  b: 2,
};
var json02 = Object.create(json);
console.log({ json });
console.log({ json02 });
console.log(json === json02); // false

function Shape() {
  this.x = 0;
  this.y = 0;
}
Shape.prototype.move = function (x, y) {
  this.x += x;
  this.y += y;
  console.log("Shape moved");
};
function RectAngle() {
  Shape.call(this);
}
RectAngle.prototype = Object.create(Shape.prototype);
var rect = new RectAngle();
console.log(rect instanceof RectAngle);
console.log(rect instanceof Shape);
rect.move(1, 1);