«Parameter Object» Pattern

If a function has more than two or three arguments, it is very easy to get confused about what is passed and in which order. The result is a very obscure code at the place of its call.

function doStuffWithBook(title, numberOfPages, downloads, rating, public) {
  // Doing something with parameters
  console.log(title);
  console.log(numberOfPages);
  // And so on
}

// ❌ What is 736? What is 10283? What is true?
doStuffWithBook("The Last Kingdom", 736, 10283, 8.38, true);

The parameter object pattern solves this problem by replacing a set of parameters with just one, an object with named properties.

function doStuffWithBook(book) {
  // Doing something with object properties
  console.log(book.title);
  console.log(book.numberOfPages);
  // And so on
}

Then, when calling, you pass one object with the necessary properties.

// ✅ Everything is clear
doStuffWithBook({
  title: "The Last Kingdom",
  numberOfPages: 736,
  downloads: 10283,
  rating: 8.38,
  isPublic: true,
});

Another advantage is that you can destructure the object in the book parameter. This can be done in the function body.

function doStuffWithBook(book) {
  const { title, numberOfPages, downloads, rating, isPublic } = book;
  console.log(title);
  console.log(numberOfPages);
  // And so on
}

Or right in the function signature, it does not make any difference.

function doStuffWithBook({
  title,
  numberOfPages,
  downloads,
  rating,
  isPublic,
}) {
  console.log(title);
  console.log(numberOfPages);
  // And so on
}