Prototypes

A prototype is the mechanism in JavaScript that makes it possible to have objects. When nothing is specified when creating a class, the objects inherit from the Object.prototype prototype. This is a rather complex built-in JavaScript class that we can use. We don't need to look at how this is implemented in JavaScript, as we can consider it the base object that is always on top of the inheritance tree and therefore always present in our objects.

There is a prototype property available on all classes, and it is always named "prototype." We can access it like this:

ClassName.prototype

Let's give an example of how to add a function to a class using the prototype property. In order to do so, we'll be using this Person class:

class Person {
  constructor(firstname, lastname) {
    this.firstname = firstname;
    this.lastname = lastname;
  }
  greet() {
    console.log("Hi there!");
  }
}

And here is how to add a function...