Lambda that receives a UserDto and returns a GreetingDto

GreetingLambda.ts

import { UserDto } from './UserDto';
import { GreetingDto } from './GreetingDto';

export const handler = async (event: any): Promise<GreetingDto> => {
  const userDto = UserDto.from(event);

  // safely access user properties
  const greeting = userDto.isFormal ?
    `Dear ${userDto.firstName} ${userDto.lastName}, welcome back.` :
    `Hey ${userDto.firstName} ${userDto.lastName}! Long time no see.`;

  return new GreetingDto(greeting);
};