declare a class in Javascript

class Car {
  constructor(make, model, color, engine) {
    this.make = make;
    this.model = model;
    this.color = color;
    this.engine = engine;
  }
}
``

This code creates a class called "Car" which is used to define objects representing an actual car. In particular, it defines the properties that all cars of this class will possess, such as make, model, color and engine. The "constructor" method is used to create new car objects, and the values supplied when creating a new car object are used to assign those properties. For example, if we wanted to create a new object representing a black Ford Mustang, we could use the code "let mustang = new Car('Ford', 'Mustang', 'black', 'V8')".