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Classes

ES6 introduced classes.

A class is a type of function, but instead of using the keyword function to initiate it, we use the keyword class, and the properties are assigned inside a constructor() method.

Example

A simple class constructor:

class Car {
  constructor(name) {
    this.brand = name;
  }
}

Notice the case of the class name. We have begun the name, "Car", with an uppercase character. This is a standard naming convention for classes.

Now you can create objects using the Car class:

Example

Create an object called "mycar" based on the Car class:

class Car {
  constructor(name) {
    this.brand = name;
  }
}

const mycar = new Car("Ford");

Note: The constructor function is called automatically when the object is initialized.

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Method in Classes

You can add your own methods in a class:

Example

Create a method named "present":

class Car {
  constructor(name) {
    this.brand = name;
  }
  
  present() {
    return 'I have a ' + this.brand;
  }
}

const mycar = new Car("Ford");
mycar.present();

As you can see in the example above, you call the method by referring to the object's method name followed by parentheses (parameters would go inside the parentheses).

Class Inheritance

To create a class inheritance, use the extends keyword.

A class created with a class inheritance inherits all the methods from another class:

Example

Create a class named "Model" which will inherit the methods from the "Car" class:

class Car {
  constructor(name) {
    this.brand = name;
  }

  present() {
    return 'I have a ' + this.brand;
  }
}

class Model extends Car {
  constructor(name, mod) {
    super(name);
    this.model = mod;
  }  
  show() {
      return this.present() + ', it is a ' + this.model
  }
}
const mycar = new Model("Ford", "Mustang");
mycar.show();

The super() method refers to the parent class.

By calling the super() method in the constructor method, we call the parent's constructor method and get access to the parent's properties and methods.

To learn more about classes, check out our section.

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