[TS: Deferred Promise] Create a promise and pass along its res and rej #typescript #javascript #promise

deferredPromise.ts

// Andrew Burgess, YouTube
// https://www.youtube.com/watch?v=Yvhad4zdPqI

export class Deferred<T, E = unknown> {
  promise: Promise<T>;
  resolve: (value: T) => void = () => null;
  reject: (reason?: E) => void = () => null;
  
  constructor() {
    this.promise = new Promise({resolve, reject} => {
      this.resolve = resolve;
      this.reject = reject;
    });
  }
}