如何从超类创建子类的实例？

Question

我正在创建一个类及其子类，需要在其中调用父级的静态方法以返回子级实例。

class Animal{
  static findOne(){
    // this has to return either an instance of Human
    // or an instance of Dog according to what calls it
    // How can I call new Human() or new Dog() here? 
  }
}

class Human extends Animal{
}

class Dog extends Animal{
}

const human = Human.findOne() //returns a Human instance
const day = Dog.findOne() //returns a Dog instance

Answer 1

该静态方法被调用，其this值是类对象，子类，你把它称为后的构造。因此，您可以使用实例化它new：

class Animal {
  static findOne() {
    return new this;
  }
}

class Human extends Animal{
}

class Dog extends Animal{
}

const human = Human.findOne() // returns a Human instance
const dog = Dog.findOne() // returns a Dog instance