PVar.ts

type PVar<T> = Promise<T> & {
  resolve: (res: T | PromiseLike<T>) => void;
  reject: (reason?: unknown) => void;
};

function mkPVar<T>() {
  const result: PVar<T> = new Promise<T>((resolve, reject) => {
    result.resolve = resolve;
    result.reject = reject;
  }) as PVar<T>;
  return result;
}

const stringsP = mkPVar<string[]>()
setTimeout(() => {
  stringsP.resolve(["asd"])
  // or `stringsP.reject("boom")`
}, 100)
  
await stringsP