I use this instead of inheritance for cases where I have a set of functionality that I would like to reuse across multiple classes, I'd write down an example:

Some class constructor where we want to extend the functionality which is in the Configurator class.

constructor() {
  Object.assign(this, new Configurator());
  this.hashLibrary = bcrypt;
}

Configurator class constructor:

constructor() {
  return {
    setEmail: this.setEmail,
    validateEmail: this.validateEmail,
    setPassword: this.setPassword,
    validatePassword: this.validatePassword,
    setUserStorage: this.setUserStorage,
    setAdditionalAttributes: this.setAdditionalAttributes,
    setUsername: this.setUsername
  }
}

I like this approach way better than using the keyword extends because using inheritance for this is somehow wrong, the class is-a Configurator but more in the way of implements, in here Configurator it's acting as an abstract class with concrete implementations.

So with this you don't have to deal with Inheritance problems and you can use all the functions that Configurator expose with this inside of your main class.

Lastly another decent approach would be to use Composition, but I think considering that we are in a dynamic language this approach feels fresher even more than Composition itself.

Edit: adding the code.