JavaScript is partly an object-oriented language.

To learn JavaScript, we got to learn the object-oriented parts of JavaScript.

In this article, we’ll go through the object-oriented parts of JavaScript.

Aggregation

The ability to combine several objects into a new one is known as aggregation or composition.

Multiple small objects are easier to manage than one large object.

There are several ways to do with JavaScript.

We can use the spread operator or Object.assign method to combine multiple objects into one.

To use the Object.assign method, we can write:

const obj1 = {
  foo: 1
}
const obj2 = {
  bar: 2
}
const obj3 = {
  bax: 3
}
const merged = Object.assign({}, obj1, obj2, obj3);

We have 3 objects, and we passed them all into Object.assign so we can merge them together and returns a new object with the properties of all of them.

Also, we can use the spread operator by writing:

const obj1 = {
  foo: 1
}
const obj2 = {
  bar: 2
}
const obj3 = {
  bax: 3
}
const merged = {
  ...obj1,
  ...obj2,
  ...obj3
};

This will also combine the 3 objects together.

Another way to aggregate objects is having child objects by having as properties of another object.

For instance, a Book object can have multiple Author objects, Publisher objects, Chapter objects, and so on.

Inheritance

Inheritance is an elegant way to let reuse existing code.

We can create objects and inherit from directly.

And we can create JavaScript classes with subclasses.

Classes and subclasses are syntactic sugar for parent and child constructor functions.

To create an object that uses another object as a prototype, we can use the Object.create method.

For instance, we can write:

const obj = {
  foo: 1
}

const child = Object.create(obj);

Then child inherits from the foo property from obj .

Most objects have the Object.prototype as their prototype if they don’t inherit from anything explicitly.

We can create subclasses with the extends keyword.

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