Snippet for my Medium article

poor-mans-web.js

const router = new KoaRouter()

router.get('/todos', async (ctx) => {
  const todosService = makeTodosService({
    todosRepository: new TodosRepository(),    
    // Our Koa request knows about the current user 
    currentUser: ctx.state.user 
  })
  
  ctx.body = await todosService.getTodos(ctx.request.query)
  ctx.status = 200
})
  
router.post('/todos', async (ctx) => {
  const todosService = makeTodosService({
    todosRepository: new TodosRepository(),
    currentUser: ctx.state.user
  })
  
  // ...
})
// and so on...

Or you can just use currying (or bind()):

export const makeTodosService = (todoRepository) => (currentUser) => { ... return todoService... }

const router = new KoaRouter()

const todoService = makeTodoService(new TodosRepository());

router.get('/todos', async (ctx) => {
  const todosService = todoService(ctx.state.user);  
  ctx.body = await todosService.getTodos(ctx.request.query)
  ctx.status = 200
})
  
router.post('/todos', async (ctx) => {
  const todosService = todoService(ctx.state.user);  
  // ...
})