Tips to write good code

Focus on content

This is 💩

              // I know it's the first step, and I know it's first result!
// I don't understand what first step is!
const result1 = doStep1();
// 💩 same as before...
const result2 = doStep2(result1);
// Come on... Get value of what? ...a? 😭
// I have to read the function bodies to understand...
// Time wasted! 🤬
const a = getValue(result2);
          

Focus on content

This is 🤩

              // Ok, now I know that you're extracting data from a UserForm
const formData = getUserFormData();
// And you're validating it
const validationErrors = validate(formData);
// And checking if we can recover errors
// without user intervention.
// I don't have to read anything else! 🍾
const shouldAskToUser = shouldPromptToUser(validationErrors);
          

Use guards clauses

Don't do this

              function saveCar(Car car, Price price, InvoiceRepo invoiceRepo): Invoice {
  if (car.isValid) {
    if (price.isBelowThreshold) {
      const invoice = prepareInvoice(car, price);
      if (invoiceRepo.isAvailable) {
        return invoiceRepo.save(invoice);
      }
      // Else everywhere!!!
      else {
        throw new InvoiceUnavailableError();
      }
      // Nesting everywhere 🤯
    }
    else {
      throw new PriceIsTooLowError(price);
    }
    // My eyes are burning! 😭
  } else {
    throw new InvalidCarError(car);
  }
}
          

Use guards clauses

Do this

              function saveCar(Car car, Price price, InvoiceRepo invoiceRepo): Invoice {
  // Guard clauses in action!
  if (!car.isValid) {
    throw new InvalidCarError(car);
  }
  if (!price.isBelowThreshold) {
    throw new PriceIsTooLowError(price);
  }
  if (!invoiceRepo.isAvailable) {
    throw new InvoiceUnavailableError();
  }

  // And then focus on business logic.
  // No nesting, no else, no messy things! 🍾
  return invoiceRepo.save(prepareInvoice(car, price));
}
          

Exploit language features

Scala: this is 🤨...

              val carWithGasolineNames = users.flatMap { user => 
  user.cars.withFilter(car => car.hasGasoline)
    .map(car => car.name)
}
          

Exploit language features

Scala: this is 🤩

              // Same as before, but using for comprehension!
val carWithGasolineNames = {
  user <- users
  car <- user.cars if car.hasGasoline
} yield car.name
          

Exploit language features

TypeScript / JS: this is 🤨...

              const newBook = Object.assign({}, defaultBook);
newBook.title = patchBook.title;
newBook.description = patchBook.description;
newBook.author = patchBook.author;
newBook.releasedAt = patchBook.releasedAt;
return newBook;
          

Exploit language features

TypeScript / JS: this is 🤩

              // Same as before, but using destructuring...
const { title, description, author, releasedAt } = patchBook;
// and spread operator!
return {
  ...defaultBook,
  title,
  description,
  author,
  releasedAt,
};
          

Exploit language features

Dart: this is 🤨...

              List additionalCars = myFriendCars;
if (myFriendCars == null) {
  additionalCars = otherFriendCars;
}
List myFavoriteCars = [];
myFavoriteCars.add(ferrari488);
myFavoriteCars.add(lamborhiniHuracan);
myFavoriteCars.add(lanciaDeltaHFIntegrale);
myFavoriteCars.addAll(additionalCars);
return myFavoriteCars;
          

Exploit language features

Dart: this is 🤩

              // Same as before, but using cascading operator (..)
return []
  ..add(ferrari488)
  ..add(lamborhiniHuracan)
  ..add(lanciaDeltaHFIntegrale)
  // and if null operator!
  ..addAll(myFriendCars ?? otherFriendCars)
          

Ask dependencies from constructor

This is 💩...

              assert('BookService should save book', () => {
  const book = new Book("id", "title", "description");
  new BookService().save(book);
  // I can't mock BookRepo dependency...
  // It's created inside BookService!
  // I have to use real BookRepo and the real DB 😭
  expect(new BookRepo().get(book.id)).toEqual(book);
});
          

Ask dependencies from constructor

This is 🤩

              assert('BookService should save book', () => {
  const book = new Book("id", "title", "description");
  const mockedBookRepo = mock(BookRepo);
  // I can pass a mocked BookRepo, test are easier now!
  new BookService(mockedBookRepo).save(book);
  expect(mockedBookRepo.save).calledOnceWith(book);
  // No DB involved, all is mocked 🍾
});
          

Avoid passing too many parameters

This is 💩...

              // To much parameters!
function filterBooks(name, description, createFrom,
                    createTo, authorEmail) {
  // I have to pass to another function
  // I have to rewrite them all! 😭
  return bookRepo.filter(
    name, description, createFrom,
    createTo, authorEmail
  );
}
          

Avoid passing too many parameters

This is 🤩

              // All parameters are inside bookFilters data class!
function filterBooks(bookFilters) {
  // Passing them is much easier now 🍾
  return bookRepo.filter(bookFilters);
}