Function todos

examples/todomvc/reducers/todos.js:10–51

(state = initialState, action)

}];

export default function todos(state = initialState, action) {
  switch (action.type) {
  case ADD_TODO:
    return [{
      id: state.reduce((maxId, todo) => Math.max(todo.id, maxId), -1) + 1,
      completed: false,
      modified: new Date(),
      text: action.text
    }, ...state];

  case DELETE_TODO:
    return state.filter(todo =>
      todo.id !== action.id
    );

  case EDIT_TODO:
    return state.map(todo =>
      todo.id === action.id ?
        Object.assign({}, todo, { text: action.text, modified: new Date() }) :
        todo
    );

  case COMPLETE_TODO:
    return state.map(todo =>
      todo.id === action.id ?
        Object.assign({}, todo, { completed: !todo.completed, modified: new Date() }) :
        todo
    );

  case COMPLETE_ALL:
    const areAllMarked = state.every(todo => todo.completed);
    return state.map(todo => Object.assign({}, todo, {
      completed: !areAllMarked, modified: new Date()
    }));

  case CLEAR_COMPLETED:
    return state.filter(todo => todo.completed === false);

  default:
    return state;
  }
}