Automate parameters passing to super()

Question

I have a parent class such as:

class Animal {
  constructor({name, color}) {
    // Does something with name and color.
  }
}

Then I have many classes that extend Animal. For example:

class Lion extends Animal {
  constructor({name, color, tailLength}) {
    super({name: name, color: color})
    // Does something with tailLength.
  }
}

My problem is that this code is not very DRY. For example, I may need to add a new parameter to Animal:

class Animal {
  constructor({name, color, height}) {
    // Does something with name, color and height.
  }
}

Now I also need to change the interface of Lion and if I have 100 more classes who extend Animal I need to change those too.

Is there a way to rewrite this code so that all parameters of Animal are implicitly added to classes that extend it?

Answer 1

Since you use a single config-like object as any animal-related constructor's sole parameter, you should make use of the rest parameter syntax in order to allow a generic and extensible approach.

class Animal {
  constructor({ name, color /* and anything the OP might furtherly want */ }) {
    // does currently something with name and color.
  }
}
class Lion extends Animal {
  constructor({ tailLength, ...configRest }) {
    super(configRest)
    // does something with tailLength.
  }
}

// usage ase e.g.
const lion = new Lion({
  name: 'Simba', color: 'yellowish'/*, height*/, tailLength: 'long',
});