Why do i keep getting undefined when accessing a inherited property?

Question

I'm trying to use prototypal inheritance and its not working, everytime i try i keep getting undefined:

function HospitalEmployee(name) {
  this._name = name;
  this._remaningVacationDays = 20;
}

function Nurse() {}

Nurse.prototype = Object.create(HospitalEmployee.prototype)

const nurseOlynyk = new Nurse("Olynyk", ["Trauma", "Genetics"])

console.log(nurseOlynyk._remainingVacationDays) //Prints undefined

What am i doing wrong?

The `Nurse` constructor doesn't call the `HospitalEmployee` constructor… — deceze, May 13 '22 at 07:08
Cause that's how it works. `new Nurse` calls the function `Nurse`, which doesn't do anything. It doesn't implicitly call `HospitalEmployee`, because there's no direct link there. Using this kind of prototypical inheritance is very bare metal. You only get this implicit behaviour with the nicer `class` syntax, which papers over all those details. — deceze, May 13 '22 at 07:15
I would suggest you to take a look at the topic "inheritance vs composition" in javascript. — MatteoPHRE, May 13 '22 at 07:16
@deceze And now JavaScript throws a referenceerror saying that HospitalEmployee is not defined when using HospitalEmployee.call() — Random User, May 13 '22 at 07:20

score 0 · Answer 1 · answered May 13 '22 at 07:34

I need use Class and Extends for it same as :

class HospitalEmployee {
  constructor(name){
    this._name = name;
    this._remaningVacationDays = 20;
  }
}
class Nurse extends HospitalEmployee {
  constructor(name, otherParams){
    super(name);
    this.otherParams = otherParams;
  }
}
const nurseOlynyk = new Nurse("Olynyk", ["Trauma", "Genetics"])
console.log(nurseOlynyk)

Why do i keep getting undefined when accessing a inherited property?

1 Answers1