TypeScript Deferred Function

Deferred.ts

type DeferredResult<DT> = { 
  promise: Promise<DT>;
  resolve: (value?: DT | PromiseLike<DT>) => void;
  reject: (reason?: any) => void;
};

type DeferredOptionalResult<DT> = {
  promise?: Promise<DT>;
  resolve?: (value?: DT | PromiseLike<DT>) => void;
  reject?: (reason?: any) => void;
};

function Deferred<DT>(): DeferredResult<DT> { 
  let deferred: DeferredOptionalResult<DT> = {}; 

  deferred.promise = new Promise<DT>((resolve, reject) => { 
    Object.assign(deferred, { resolve, reject })
  }); 

  return deferred as DeferredResult<DT>;
}