js instanceof

检测构造函数的 prototype 属性是否出现在某个实例对象的原型链上。

function Car(make, model, year) {
  this.make = make;
  this.model = model;
  this.year = year;
}
const auto = new Car('Honda', 'Accord', 1998);

console.log(auto instanceof Car);
// expected output: true

console.log(auto instanceof Object);
// expected output: true

class PersonClass {
    // 等价于 PersonType 构造器，自有属性
    constructor(name) {
        this.name = name;
    }
    // 等价于 PersonType.prototype.sayName
    sayName() {
        console.log(this.name);
    }
}
let person = new PersonClass("Nicholas");
person.sayName(); // 输出 "Nicholas"
console.log(person instanceof PersonClass); // true
console.log(person instanceof Object); // true
console.log(typeof PersonClass); // "function"
console.log(typeof PersonClass.prototype.sayName); // "function"