Optionalonfinally: null | (() => void)Optionalreason: anyOptionalonfulfilled: The callback to execute when the Promise is resolved.
Optionalonrejected: null | ((reason: any) => TResult2 | PromiseLike<TResult2>)The callback to execute when the Promise is rejected.
A Promise for the completion of which ever callback is executed.
Attaches callbacks for the resolution and/or rejection of the Promise.