JavaScript : Inherit constructor properties from Parent Class

Question

Lets assume i have a baseclass and i want to inherit the properties from the constructor.

Note: This is an example code. It is not intended to work or anything, just to demonstrate my problem

Base Class

class BaseClass {
    constructor(a, b) {
        this.a = a;
        this.b = b;
    }
    
    /* SOME CLASS METHODS */ }

Myclass

class Myclass extends BaseClass {
    constructor() {
        super();
    };

/* SOME CLASS METHODS */ }

MyProblem

let test = Myclass('dog', 'cat');

However, this doesnt seem to work. Why does the Myclass-constructor not initialize the BaseClass constructor? When i look at the debugger for this.a and this.b, this values are undefined.

HenriDev · Accepted Answer · 2020-06-26 09:05:50Z

3

you need to pass through an a and b value to the super method

like here:

class Myclass extends BaseClass {
    constructor(a, b) {
        super(a, b);
};

super

answered Jun 26, 2020 at 9:05

HenriDev

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Comments

deceze · Accepted Answer · 2020-06-26 09:06:11Z

2

constructor() {
    super();
};

Your child class is overriding the constructor, is not accepting any arguments, and passes no arguments to the parent constructor (super()), so all parameters in the parent constructor are undefined. Your child constructor needs to accept the same or more parameters, and/or provide default arguments to super().

In this particular case, the child constructor doesn't do anything, so may as well be omitted entirely.

answered Jun 26, 2020 at 9:06

deceze♦

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