Typescript Promise that can be resolved/rejected externally

OuterPromise.ts

/**
 * Created by Dimitris Vlachakis (TheCrafter) on 11/9/2019
 * https://github.com/TheCrafter
 * https://gist.github.com/TheCrafter/418401b6ad59fa0190a6d9ab4d5f9fb2
 * 
 * Example: https://www.typescriptlang.org/play/?strictPropertyInitialization=false#code/PQKhCgAIUhhAnApgQwC6ICaQEYE9IAiAlgLZGrxEDOkAagDbIDGAFsgNbWQAUAKi4gTIAZungBKSAHsAdpACM84AE5gAJgAM85VBgtUqAA5UAXMGABzciwCu2AHRMpJYP0HwRY3ZH1HT5qypUeytUWwcnFzchUUR4YAAWeQAOBK1sADZkDABWZWFkLWUNZAyMZWRsBNzhfOw1b11vAGVSQ3pESAB3D0NDOMhUKUhkenopLsgkKil6ADciGQsRyEN4Z2pOxAAPMRlR+lx7XWBwcHNIAFVUInpIYRsZJhvZQeHWRCZ2e6l4SBkbGNpH9HhhEMJFphIHNRjZEFR7JAAEqIdrMTpdayQXBSGx-CYyY4PJ4vORg4TcKTYABWJhGMlwkgA3lApohUHi5ABCSk0yAAXkF-0BdwAPqLpHzBfzIKDwZCMOIANzgAC+Z1AEGgkAAgt1ev0-sh1qDIAAFdZkKidMJoEZjCY0IZsmbzRDAJDUz6oSDkSA7PYHI6QNxIX00UYzbzISAAImm7NjkBInzYMmoJF9JHaiBTMnQWBm3U6GFkAHIfWw5jbhkgALRMJBoG0CSAAeRsYgtG2tkq9z28RGExcg1JsQW6yHzbzZdfHnXIx21vGGQWNPvHi2WfpxNn+iChzsQ1gGTAOLvZ3EknlPTZuS0Grap-Z9v1WyCoVC3g3gcOjNEMY1kBTMQfj+BNUAASRkWBZCCX9njfLoBDkRsUHvZYwk6Z9vURfg0DLGhsE+ZB50gGYQNIeERxIZBcG8GQDywZ0wUYfAsN9GQ13zIg0CIV4pGHDi1h7TpHhuO5GDEJcYAAdRQx9OhEq0FyoGQK0gNDmywXB2QAGkUydyCve5Hmefi5CQDl4C4+l-WzVB8GmWZqywbsVJk04mEYT9207OJ3M2AAeXgBXpXADIAUTCqdcAAPkgFlIFWSgYXQFLRLpQLrRCuKlUgC5MSBKgWAmEYaDidY-kxMJcR9WN4KIZ5u0NRzoPIXj6CIAAvPjZFjOkCnoXtFkGKgnBkCELHsakZhkVk1iINLsP8+AUVdas6W4GF6DhAB+OlQolbLEAAGSIdhEFyyR+QSuYpCILAZSvW6mVVFVksW5bpFWlEXy2ps5oOyBIpuu6HqenhxFe96FtS5tIAAfWoM1EBkDBvxlIbrQ+lKloR5GqD+70oSxyNEFxr6CeoAAxQEITGUn7nJlVWQm+CbEQ+BuAg6DYK4ihOaGeA6WwKRZhQOQyeGxBmVZZKhx4XmYLgwWubl5LNcfah7Agq9ceS9VDbOT67C6pgXRcxBtthRBgaO81LU2c7LuuxL5d9YduHJbgwh15TNnEDWte1hE6ridarZt3bZYNyAjfjk3VjNpq2RfHmUCBulQfdrXFe98FfZYf2netIPc5Dv2w9+xB08B2RlQ91V1VZTV5ZgFFrNsjjFi-MEMpU4E7NzQxHMtt0sADkahNbXvHqU0uSykeF1J9HZqB9XTgnb3VhuGA5HRna0fRjG4UzqsCRk7KQ62c+Zv2Exel2SmAADkpHQEwd4IB6H1jZAujID9CQXAHYuxP0AcZeQGgYHKiTCmKcTo2Cb1xN0W4dxIE+mEG+R+okZyRUgrwAAEpFJEOBEA7zvq5aQchyA0AJO2MhxEr7OioVCG8fxoEwOTNaJgz9oA7wAAKAQ8JmM+iAL68CopxHhnwZyYPIdgsMpFWHwhcg-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-tDrapOQGjkW0QIwYw2bd2OLiS01DczYPpTrMsp9b70Mt2JOZV4rE6LcBIKYM9cTg4oatUWyFjtRLcHHtWBV5F2TLrqhnLZBkWOSEbi3Dor55AQsQJMc58ATq+1-LHcAcnpBqEU8p1aanBWN201QXtNNxYxSoLgJ4PApBnIM4velrIAFAJ9Ix3A3BNCwNxlITZUcZNnG0+IkWIY716dCymbmjdgubMvI3UzExzNSEpPIRuUh5D2EwVealKF5XNOqezCW9hxgWG4AAA3SwJ9hsQ-gABImQxdA+B8Q9gcPIDwxgK8qpZFMDKzJslFwpC6aKncZhbCsAQngBOYiZ49xdE6NkMEWBT6RM7DQsJV5wAxZOSqBLXQkuUjUGltQmXXPcByLAnLaM8uKuSoVjoxWpClYq7p8bIwauQHq41oYzXWu4etJ18Q3WWOfD6yqUlSogA
 *
 * Simple wrapper to allow resolving a promise externally.
 */

// Util function to check for null or undefined values. Replace with your own.
function def(obj) {
  return !(obj === null || obj === undefined);
}

/**
 * A wrapper around Promise that allows to resolve/reject it externally. There is also
 * a "reset" mechanism implemented so we don't have to re-create the OuterPromise object
 * if we just want to re-use it.
 * To start using it you need to either call reset() after creating the object or passing true
 * as parameter for resetInConstructor when creating the object. That's because sometimes we may
 * need to delay the instantiation of the promise until later.
 * When the promise isn't created yet, the wait() function returns an empty resolved Promise.
 */
export class OuterPromise<T = any, E = any> {
  private promise: Promise<T>; // will show as error without "strictPropertyInitialization": false in tsconfig.json
  private outerResolve: (value?: T | PromiseLike<T>) => void = ()=>{};
  private outerReject: (reason?: E) => void = ()=>{};
  private _isPending = false;
  private _isRejected = false;
  private _isFulfilled = false;

  constructor(resetInConstructor: boolean = false) {
    if (resetInConstructor) {
      this.reset();
    }
  }

  public resolve(value?: T | PromiseLike<T>) {
    if (def(this.promise)) {
      this.outerResolve(value);
    }
  }

  public reject(reason?: E) {
    if (def(this.promise)) {
      this.outerReject(reason);
    }}

  /**
   * Returns the inside promise or an empty resolved promise if the inside promise doesn't exist yet.
   * Also allows to set a timeout for auto-resolving the promise.
   * Note:
   * Doing "await myOuterPromise.wait(1000);" means that you will wait for the promise to EITHER be
   * resolved on its own OR be auto resolved after 1000 msec.
   *
   * @param timeout Time in msec to wait before auto resolving the promise
   * @param autoResolveValue A value to pass as argument when automatically resolving the promise
   */
  public wait(timeout?: number, autoResolveValue?: T) : Promise<T> {
    if (def(timeout) && def(this.promise)) {
      setTimeout(() => {
        this.resolve(autoResolveValue);
      }, timeout);
    }

    return def(this.promise) ? this.promise : Promise.resolve({} as T);
  }

  public reset(): OuterPromise<T> {
    this._isPending = true;
    this._isFulfilled = false;
    this._isRejected = false;

    this.promise = new Promise<T>((resolve, reject) => {
      this.outerResolve = resolve;
      this.outerReject = reject;
    });

    this.promise
    .then(() => {
      this._isPending = false;
      this._isFulfilled = true;
      this._isRejected = false;
    })
    .catch(() => {
      this._isPending = false;
      this._isFulfilled = false;
      this._isRejected = true;
    });

    return this;
  }

  get isPending():   boolean { return this._isPending;   }
  get isRejected():  boolean { return this._isRejected;  }
  get isFulfilled(): boolean { return this._isFulfilled; }
}