Why private static methods are important

private-static-1.js

// Today, with underscore-prefixed "private"

class Point {
  constructor(x, y) {
    this._x = x;
    this._y = y;
  }
  
  length() {
    return Math.sqrt(squareLengthHelper(this));
  }
}

function squareLengthHelper(point) {
  return point._x ** 2 + point._y ** 2;
}

export default Point;

private-static-2.js

// In the future, with real private

class Point {
  #x, #y;
  
  constructor(x, y) {
    this.#x = x;
    this.#y = y;
  }
  
  length() {
    return Math.sqrt(Point.#squareLengthHelper(this));
  }
  
  static #squareLengthHelper(point) {
    return point.#x ** 2 + point.#y ** 2;
  }
}

// ok, but after writing this, I realized that #squareLengthHelper is better as an instance method...