javascript - Using a constructor function in the same way a class extends works?

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65850821/using-a-constructor-function-in-the-same-way-a-class-extends-works

Answer 1

With the class, the prototype chain for an Athlete is:

instance <- Athlete.prototype <- Person.prototype

With Functions, the internal prototype of instances is the .prototype property on the function used to construct it. Just like with classes, the internal prototype of new Foo() will be Foo.prototype. So, to extend it manually, you need to set the .prototype property to an object that inherits from Person.prototype:

function Person(name, age, speciality = "Not Specified") {
  this.name = name;
  this.age = age;
  this.speciality = speciality;
}
Person.prototype.sayName = function() {
  return this.name;
}

function Athlete(name, age, speciality) {
  Person.call(this, name, age, speciality);
  this.speciality = speciality;
}

Athlete.prototype = Object.create(Person.prototype);
Athlete.prototype.getSport = function() {
  return "I play " + this.speciality;
};



let jim = new Athlete('jim', 54, 'basketball');
console.log(jim.sayName());
console.log(jim.getSport());