Redux操作类型的字符串与常量

// 定义操作类型的常量
const ADD_TODO = 'ADD_TODO';
const DELETE_TODO = 'DELETE_TODO';
const UPDATE_TODO = 'UPDATE_TODO';

// 定义action创建函数
function addTodo(todo) {
  return {
    type: ADD_TODO,
    payload: todo
  };
}

function deleteTodo(id) {
  return {
    type: DELETE_TODO,
    payload: id
  };
}

function updateTodo(id, todo) {
  return {
    type: UPDATE_TODO,
    payload: { id, todo }
  };
}

// 定义reducer
function todosReducer(state = [], action) {
  switch (action.type) {
    case ADD_TODO:
      return [...state, action.payload];
    case DELETE_TODO:
      return state.filter(todo => todo.id !== action.payload);
    case UPDATE_TODO:
      return state.map(todo => {
        if (todo.id === action.payload.id) {
          return { ...todo, ...action.payload.todo };
        }
        return todo;
      });
    default:
      return state;
  }
}

// 使用Redux store
const store = Redux.createStore(todosReducer);

// 分发action
store.dispatch(addTodo({ id: 1, text: 'Buy groceries' }));
store.dispatch(deleteTodo(1));
store.dispatch(updateTodo(2, { text: 'Finish homework' }));