Build Applications with Meteor

The reducer function

We start with the action type INITIAL_LOAD:

export default function cards(state = [], action) {    switch (action.type) {    case INITIAL_LOAD:       return action.data;

Here, we return the new data; notice we do not mutate our state. The second one is the ADD_CARD action:

case ADD_CARD:if (state.filter(card => card._id === action.id).length > 0) {      return state; }   return [    ...state, {    _id: action.id,    title: action.title,    task: action.task,    status: action.status   } ]

In our app, when we create a new card, we dispatch the ADD_CARD action, and at the same time, we listen for collection changes. Since we are changing the collection (adding a new card), we will dispatch the RECEIVE_CARD action. To prevent adding one item twice, we ...