Parameter Object

When classes require multiple pieces of data to initialize an object, managing several individual parameters can quickly become complex and error-prone.

Using a Single Object as a Parameter

When creating complex objects, passing multiple parameters into a class constructor can become cumbersome and error-prone. A clean solution is using a parameter object, where you pass a single object containing all the necessary properties. This approach keeps your code organized and reduces the risk of mistakes, especially when the number of parameters grows.

Think of it like placing an order for a custom-built car. Instead of telling the manufacturer every detail - such as the color, engine type, interior material, and other features - one by one, you provide a specification sheet (an object) that contains all these details at once. It’s more efficient and less prone to errors.

Instead of defining multiple parameters in the constructor, you accept a single object that holds all the data needed for initialization.


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class Animal {
  constructor({ name, type, age, diet }) {
    this.name = name;
    this.type = type;
    this.age = age;
    this.diet = diet;
  }

  // Method to describe the animal
  getInfo() {
    return `${this.name} is a ${this.age}-year-old ${this.type} animal that follows a ${this.diet} diet.`;
  }
}

const lion = new Animal({
  name: 'Lion',
  type: 'Wild',
  age: 12,
  diet: 'Carnivore',
});

console.log(lion.getInfo()); // Output: Lion is a 12-year-old Wild animal that follows a Carnivore diet.

In this example, instead of passing name, type, age, and diet as separate parameters, we pass a single object to the constructor. This method makes the class easier to manage, especially as the number of properties grows.

Benefits of Passing a Parameter Object

1. Readability and Clarity

Passing an object makes the function call more readable. You can immediately see what values correspond to which properties without relying on the order of the parameters.

In comparison with:

When you pass multiple values in the second example, it isn't immediately obvious which values correspond to which properties without referring to the constructor definition. The parameter object approach improves clarity.

2. Flexibility

Using a parameter object allows you to skip certain properties or add new ones without changing the function signature. This makes the constructor more adaptable, particularly when you need to handle optional parameters.

In this case, we're only passing name and age without type or diet. If these properties are optional in your class, you can easily manage them by defaulting to certain values or leaving them undefined.

1. Which of the following correctly demonstrates using a parameter object in a `constructor`?

2. Given the following class definition, how would you instantiate a new `Animal` object called `rabbit` with only `name` and `age` using a parameter object?

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Seção 1. Capítulo 6