then

expect fun <S : JsAny?> then(onFulfilled: (T) -> S?): Promise<S>

expect fun <S : JsAny?> then(onFulfilled: (T) -> S?, onRejected: (JsAny) -> S?): Promise<S>

actual fun <S : JsAny?> then(onFulfilled: (T) -> S?): Promise<S>

actual fun <S : JsAny?> then(onFulfilled: (T) -> S?, onRejected: (JsAny) -> S?): Promise<S>