I have a JavaScript ES6 class in a library that uses some private base values to compute another value.

Abstracted and simplified the situation is something like this:

class Example {
  #apples;
  #oranges;
  #cherries;

  constructor() {
    this.#apples = 22;
    this.#oranges = 38;
    this.#cherries = 12;
  }

  get numOfFruits() {
    return this.#apples + this.#oranges + this.#cherries;
  }
}

Now I want to add a function to Example to compute a new value e.g. something like:

Example.prototype.getNumOfApplesAndOranges = function() {
   return this.#apples + this.#oranges;
};

I get that you are not supposed to access private variables outside their declaring class but I thought that by adding a method to the class the access happens within the class.

However this does not work and errors with Uncaught SyntaxError: reference to undeclared private field or method #apples. Is there any way to make this work?

I already tried with eval, Proxy and Object.setPrototypeOf but none of these helped.