Question

To me classes are quite similar to NodeJS (CommonJS) modules. You can have many of them, they can be reused, they can use each other and they are generally one-per-file.

What makes modules so different from classes? The way you use them differs, and the namespace difference is obvious. Besides that they seem very much the same thing to me or perhaps I am just not seeing the obvious benefit here.

Answer 1

Modules are more like packages (to use the Java term) than classes. You don’t instantiate a module; there is only one copy of it. It’s a tool for organizing related functionality, but it doesn’t typically encapsulate the data of a particular instance of an object.

Probably the closest analogue to a class (setting aside those libraries that actually construct class-based inheritance in JavaScript) is just a constructor function. You can of course put such functions inside a module.

function Car() {
    this.colour = 'red';
}
Car.prototype.getColour = function() { return this.colour; };

var myCar = new Car();
myCar.getColour(); // returns 'red'

You use both modules and classes for encapsulation, but the nature of that encapsulation is different.