Redux basic pattern #redux

redux-basic-pattern.js

// state:
const state = {
  todos: [{
    text: 'Eat food',
    completed: true
  }, {
    text: 'Exercise',
    completed: false
  }],
  visibilityFilter: 'SHOW_COMPLETED'
};

// Actions:
const ADD_TODO = { type: 'ADD_TODO', text: 'Go to swimming pool' };
const TOGGLE_TODO = { type: 'TOGGLE_TODO', index: 1 };
const SET_VISIBILITY_FILTER = { type: 'SET_VISIBILITY_FILTER', filter: 'SHOW_ALL' };

// "Partial" reducers:
// Each reducer manages a part of the state
function visibilityFilter(state = 'SHOW_ALL', action) {
  if (action.type === 'SET_VISIBILITY_FILTER') {
    return action.filter
  } else {
    return state
  }
}

function todos(state = [], action) {
  switch (action.type) {
    case 'ADD_TODO':
      return state.concat([{ text: action.text, completed: false }])
    case 'TOGGLE_TODO':
      return state.map(
        (todo, index) =>
          action.index === index
            ? { text: todo.text, completed: !todo.completed }
            : todo
      )
    default:
      return state
  }
}

// Global reducer:
function todoApp(state = {}, action) {
  return {
    todos: todos(state.todos, action),
    visibilityFilter: visibilityFilter(state.visibilityFilter, action)
  }
}