Interface is a skeleton something should conforms to. In general, interfaces are skeletons for classes. But need to explicitly mention that class implements the interface. If the class conforms on the interface is checked on the compile-time. But since, in JavaScript almost everything is an object. Interface is a skeleton for an object. Since class is also an object, and everything is covered. Unlike in other languages, interface can be used with any object at the compile-time, and checked if it conforms with the interface.