Reducer with immutable.js

reducer_immutable.js

function tasksReducer (state = Map(), action) {
  switch (action.type) {
    case ADD_TASK:
      return state.set(action.task.id, action.task)

    case REMOVE_TASK:
      return state.delete(action.id)
      
    case COMPLETE_TASK:
      return state.updateIn([action.id, 'completed'], true)

    default:
      return state
  }
}