ES6 classes do not work exactly the same way as in other object oriented languages.
A class in ES6 is a function under the hood.
class in ES6 is syntactical sugar over Objects and Prototypes.
This new class keyword in ES6 supports prototype-based inheritance, constructors, super calls, instance, and static methods.
The following code uses the most basic form of class declaration in ES6.
class Car {
constructor(brand) {
this.brand = brand;
}
}
const myTesla = new Car("Tesla");
console.log(myTesla.hasOwnProperty("brand")); // true
console.log(typeof Car); // function
Here, brand is the property assigned on the myTesla object.
This object can be represented in an object literal form as follows:
const myTesla = {
brand: "Tesla"
};
The constructor() method is optional, you can declare an empty class like the one in the following example:
class EmptyClass {
}
If you don't define a constructor() method inside a class, the JavaScript engine will insert an empty one for you:
class EmptyClass {
/* JavaScript inserts an empty constructor:
constructor () { }
*/
}
Class declarations allow you to define methods on a class without the use of a "function" keyword:
class Car {
constructor(brand) {
this.brand = brand;
}
start() {
console.log(`Your ${this.brand} is ready to go!`);
}
}
const myTesla = new Car("Tesla");
myTesla.start();
// Your Tesla is ready to go!
Here, we defined a start() method inside the class definition, which accesses the brand property of the class using this keyword.
This method gets automatically attached to the class's prototype and hence is non-enumerable.