Class Keyword in JavaScript

JavaScript classes, introduced in ES6, are syntactical sugar over JavaScript prototype-based inheritance. Classes are in fact "special functions". You can define classes in JavaScript using the class keyword using the following syntax −

class Person {
   // Constructor for this class
   constructor(name) {
      this.name = name;
   }
   // an instance method on this class
   displayName() {
      console.log(this.name)
   }
}

This is essentially equivalent to the following declaration −

let Person = function(name) {
   this.name = name;
}
Person.prototype.displayName = function() {
   console.log(this.name)
}

This class can also be written as a class expressions. The above format is a class declaration. The following format is a class expression −

// Unnamed expression
let Person = class {
   // Constructor for this class
   constructor(name) {
      this.name = name;
   }
   // an instance method on this class
   displayName() {
      console.log(this.name)
   }
}

No matter how you define the classes as mentioned above, you can create objects of these classes using the following −

Example

let John = new Person("John");
John.displayName();

Output

John

You can read in depth about JS classes and the class keyword at https://www.tutorialspoint.com/es6/es6_classes.htm.