Redux 是一个可预测的状态容器，基于三个核心原则构建：一个单一存储、只读状态（只能通过actions改变）和纯reducer（计算下一个状态）。数据单向流动，使所有更改都可以追踪。
1. Single source of truth — the whole app's state lives in ONE store object
2. State is read-only — you never mutate it; you DISPATCH actions to change it
3. Changes via pure reducers — (state, action) => newState, no side effects
// STORE — holds the single state tree
const store = configureStore({ reducer: rootReducer });
// ACTION — a plain object describing what happened
const action = { type: "counter/incremented", payload: 1 };
// REDUCER — pure function: given state + action, returns NEW state
function counterReducer(state = { value: 0 }, action) {
switch (action.type) {
case "counter/incremented":
return { ...state, value: state.value + action.payload }; // new object
default:
return state;
}
}
// DISPATCH — the only way to trigger a change
store.dispatch(action);
// SELECT — read state
store.getState().counter.value;
UI dispatches an ACTION → REDUCER computes new STATE → STORE updates →
subscribed components re-render → user interacts → dispatches the next action
这种严格的单向流意味着每个状态改变都是由分发的action通过纯函数处理的结果——完全可追踪。
import { useSelector, useDispatch } from "react-redux";
function Counter() {
const count = useSelector(state => state.counter.value); // read
const dispatch = useDispatch();
return <button onClick={() => dispatch(increment())}>{count}</button>; // write
}
Predictability — every change is an explicit, logged action
Debuggability — time-travel debugging, action replay (Redux DevTools)
Testability — pure reducers are trivial to unit test
（注：现代Redux使用Redux Toolkit，它大幅减少了样板代码，同时保留了这些核心概念。）
Redux的核心概念——单一存储、actions、纯reducer、单向流——使应用状态可预测且可追踪，这是它对大型应用的主要价值所在。
理解store/action/reducer/dispatch/select对于许多使用Redux的代码库至关重要，而这些原则（不可变更新、纯reducer、单向数据流）在几乎所有状态管理库中都会重复出现。
权衡是样板代码，Redux Toolkit在保留这些基础原则的同时解决了这个问题。