Similar to UserDto, but with other properties

GreetingDto.js

export class GreetingDto {
  static from(input: unknown) {
    const parsedInput = typeof input === 'string' ? JSON.parse(input) : input;
    
    if(!GreetingDto.isValid(parsedInput)) {
      throw Error('Invalid input type');
    }
    
    const { greeting } = parsedInput;

    return new GreetingDto(greeting);
  }

  protected static isValid(input: any) : input is GreetingDto {
    return (
      typeof input.greeting === 'string'
    );
  }

  constructor(
    readonly greeting: string,
  ) { }
  
  serialize() {
    return JSON.stringify(this);
  }
}