class Singleton {
    test;
    constructor() {
    if(typeof Singleton.instance === 'object') { //if object instance already exists
        return Singleton.instance;  //return object reference
    }
    Singleton.instance = this;  //else store object instance
    return this;    //and return this
    }
  
    get test() {
      return this.test;
    }
    
    set test(value) {
      this.test = value;
    }
}

var obj1 = new Singleton();
var obj2 = new Singleton();
obj1.test = 1;
obj2.test;

console.log(obj1 === obj2);
console.log(obj2.test);

class State {
    private static instance: State;
    private _token: string;
    constructor() {
        this._token = '';
        if (typeof State.instance === 'object') {
            return State.instance;
        }
        State.instance = this;
        return this;
    }

    get token() {
        return this._token;
    }

    set token(value: string) {
        this._token = value;
    }

    set refreshToken(value: string) {
        this._refreshToken = value;
    }

    set userId(value: string) {
        this._userId = value;
    }

    set name(value: string) {
        this._name = value;
    }

    set message(value: string) {
        this._message = value;
    }

    toJSON() {
        return {
            token: this.token,
        };
    }
}