Private instance methods and accessors

PrivateInstanceMethods.js

class Banner extends HTMLElement {
  // Private variable that cannot be reached directly from outside, but can be modified by the methods inside:

  #slogan = "Hello there!"
  #counter = 0

  // private getters and setters (accessors):

  get #slogan() {return #slogan.toUpperCase()}
  set #slogan(text) {this.#slogan = text.trim()}

  get #counter() {return #counter}
  set #counter(value) {this.#counter = value}

  constructor() {
    super();
    this.onmouseover = this.#mouseover.bind(this);
  }

  // private method:
  #mouseover() {
    this.#counter = this.#counter++;
    this.#slogan = `Hello there! You've been here ${this.#counter} times.`
  }
}