实例方法

hasOwnProperty()

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方法返回一个布尔值，表示对象自有属性（而不是继承来的属性）中是否具有指定的属性

const object1 = {};
object1.property1 = 42;

console.log(object1.hasOwnProperty('property1'));
// Expected output: true

console.log(object1.hasOwnProperty('toString'));
// Expected output: false

console.log(object1.hasOwnProperty('hasOwnProperty'));
// Expected output: false

isPrototypeOf()

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方法用于检查一个对象是否存在于另一个对象的原型链中

function Foo() {}
function Bar() {}

Bar.prototype = Object.create(Foo.prototype);

const bar = new Bar();

console.log(Foo.prototype.isPrototypeOf(bar));
// Expected output: true
console.log(Bar.prototype.isPrototypeOf(bar));
// Expected output: true

propertyIsEnumerable()

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方法返回一个布尔值，表示指定的属性是否是对象的可枚举自有属性

const object1 = {};
const array1 = [];
object1.property1 = 42;
array1[0] = 42;

console.log(object1.propertyIsEnumerable('property1'));
// Expected output: true

console.log(array1.propertyIsEnumerable(0));
// Expected output: true

console.log(array1.propertyIsEnumerable('length'));
// Expected output: false

toLocaleString()

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方法返回一个表示对象的字符串。该方法旨在由派生对象重写，以达到其特定于语言环境的目的

const date1 = new Date(Date.UTC(2012, 11, 20, 3, 0, 0));

console.log(date1.toLocaleString('ar-EG'));
// Expected output: "٢٠‏/١٢‏/٢٠١٢ ٤:٠٠:٠٠ ص"

const number1 = 123456.789;

console.log(number1.toLocaleString('de-DE'));
// Expected output: "123.456,789"

toString()

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方法返回一个表示该对象的字符串。该方法旨在重写（自定义）派生类对象的类型转换的逻辑

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

const dog1 = new Dog('Gabby');

Dog.prototype.toString = function dogToString() {
  return `${this.name}`;
};

console.log(dog1.toString());
// Expected output: "Gabby"

valueOf()

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方法将 this 值转换成对象。该方法旨在被派生对象重写，以实现自定义类型转换逻辑

function MyNumberType(n) {
  this.number = n;
}

MyNumberType.prototype.valueOf = function () {
  return this.number;
};

const object1 = new MyNumberType(4);

console.log(object1 + 3);
// Expected output: 7