JavaScript/Typescript Singleton

snippet programming

class Singleton {
  protected static instance: Singleton | null;

  protected constructor() { // <-- Important to make it *private*
    this.id = Math.random();
  }

  public static getInstance(): Singleton {
    if (!Singleton.instance) {
      Singleton.instance = new Singleton();
    }

    return Singleton.instance;
  }

  private id = 0;
  getId() {
    return this.id;
  }
}

const classes = [
  Singleton.getInstance(),
  Singleton.getInstance(),
  Singleton.getInstance(),
  Singleton.getInstance(),
];

for (const c of classes) {
  console.log(`c: `, c);
  console.log(`c.id: `, c.getId());
  console.log("----------------");
}