Demo: Equipment desk checkout

Equipment desk checkout

A community equipment desk loans kits. The base class keeps its loan status private and exposes guarded methods. A specialized camera kit inherits those rules and adds its own description. Run the checkout twice, then return it.

javascript

class Equipment {
  #onLoan = false;
  constructor(label) { this.label = label; }
  checkout() {
    if (this.#onLoan) return false;
    this.#onLoan = true;
    return true;
  }
  returnItem() {
    if (!this.#onLoan) return false;
    this.#onLoan = false;
    return true;
  }
  get available() { return !this.#onLoan; }
  describe() { return `${this.label}: ${this.available ? "ready" : "on loan"}`; }
}
class CameraKit extends Equipment {
  constructor(label, lens) {
    super(label);
    this.lens = lens;
  }
  describe() { return `${super.describe()} (${this.lens} lens)`; }
}
const kit = new CameraKit("Travel camera", "wide");
console.log(kit.checkout());
console.log(kit.checkout());
console.log(kit.describe());
kit.returnItem();
console.log(kit.describe());

What to notice

Remove the return call and run again. Next, build a different library book checkout model yourself.

Demo: Equipment desk checkout

Equipment desk checkout

javascript

class Equipment {
  #onLoan = false;
  constructor(label) { this.label = label; }
  checkout() {
    if (this.#onLoan) return false;
    this.#onLoan = true;
    return true;
  }
  returnItem() {
    if (!this.#onLoan) return false;
    this.#onLoan = false;
    return true;
  }
  get available() { return !this.#onLoan; }
  describe() { return `${this.label}: ${this.available ? "ready" : "on loan"}`; }
}
class CameraKit extends Equipment {
  constructor(label, lens) {
    super(label);
    this.lens = lens;
  }
  describe() { return `${super.describe()} (${this.lens} lens)`; }
}
const kit = new CameraKit("Travel camera", "wide");
console.log(kit.checkout());
console.log(kit.checkout());
console.log(kit.describe());
kit.returnItem();
console.log(kit.describe());

What to notice

Remove the return call and run again. Next, build a different library book checkout model yourself.