Service without dependencies

A service without dependencies is a service whose constructor is empty:

export Service {
  constructor(){}
  getData() {}
}

To use it, you simply type:

import { Service } from './service'
let service = new Service();
service.getData();

Any module that consumes this service will get their own copy of the code, with this kind of code. If you, however, want consumers to share a common instance, you change the service module definition slightly to this:

class Service {
  constructor() {}
  getData() {}
}
const service = new Service();
export default service;

Here, we export an instance of the service rather than the service declaration.