Accessing Parent Methods in Javascript Classes

I recently got to do Object-Oriented programming in Javascript. Many of the Javascript features resemble Java language (class, super, extends and static keywords to name a few).

One of the differences with Java is that super() will not be called implicitly in child class so you must call it explicitly always when extending a class.

Another interesting issue I ran into is that if super.someMethod() is called from a child class, then someMethod must not be implemented as an arrow function. For example, the code below will trigger an error:

class Car {
  drive = () => "drive"
}

class FastCar extends Car {
  drive = () => super.drive() + " fast"
}

const fastCar = new FastCar()
console.log(fastCar.drive())

The error is TypeError: Cannot read property 'call' of undefined will occur on the invocation of the line console.log(fastCar.drive()). The error occurs because the drive method in Car is implemented as an arrow function. As per this stackoverflow answer a class method implemented as an arrow function become a property with function type while a method implemented as a regular function stays a class method. So while methods are stored in class prototype, properties are only accessible on class instances. Therefore the correct implementation is as follows:

class Car {
  drive() {
    return "drive"
  }
}

class FastCar extends Car {
  drive = () => super.drive() + " fast"
}

const fastCar = new FastCar()
console.log(fastCar.drive())