My own promise-like object where I can type the rejection and I can resolve from the outside

deferred.ts

export class Deferred<T = void, E = Error> {
  #promise: Promise<T>
  // deno-lint-ignore ban-ts-comment
  // @ts-ignore
  resolve: (arg: T) => void
  // deno-lint-ignore ban-ts-comment
  // @ts-ignore
  reject: (arg: E) => void

  constructor() {
    this.#promise = new Promise<T>((res, rej) => {
      this.resolve = res
      this.reject = rej
    })
  }

  then<F, R>(onFulfilled: (arg: T) => F, onRejected?: (arg: E) => R) {
    return this.#promise.then(onFulfilled, onRejected)
  }

  catch<F>(cb: (arg: E) => F) {
    return this.#promise.catch(cb)
  }

  finally(cb: () => void) {
    return this.#promise.finally(cb)
  }
}