Snippet for my Medium article

todosRepository.js

// Let's do an in-memory implementation for now.
const _todos = []

export default class TodosRepository {
  // Marking all methods async makes them return promises!
  async find(query) {
    const filtered = _todos.filter((todo) => {
      // Check the user ID
      if (todo.userId !== query.userId) 
        return false
      // Check the filter
      if (query.filter === 'COMPLETED') 
        return todo.completed === true
      if (query.filter === 'INCOMPLETED') 
        return todo.completed === false
      return true
    })
    
    return filtered
  }
  
  async get(id) {
    const todo = _todos.find(x => x.id === id)
    return todo
  }
  
  async create(data) {
    const newTodo = {
      id: Date.now(), // cheeky ID generation
      text: data.text,
      userId: data.userId,
      completed: data.completed
    }
    _todos.push(newTodo)
    return newTodo
  }
  
  async update(id, data) {
    const todo = await this.get(id)
    Object.assign(todo, data)
    return todo
  }
  
  async delete(id) {
    const todo = await this.get(id)
    const idx = _todos.indexOf(todo)
    if (idx === -1) return
    _todos.splice(idx, 1)
  }
}