Here is the COMPLETE internal Redux flow diagram + exact internal code that explains everything end-to-end exactly how Redux works under the hood.
I’m giving:
✅ ASCII Diagram (Very clear)
✅ Internal store implementation (exact how Redux behaves)
✅ Internal middleware pipeline code
✅ Internal react-redux subscription model
✅ Internal Redux Toolkit slice generator code (simplified)
🎯 1. FULL REDUX INTERNAL FLOW DIAGRAM
┌─────────────────────────────┐
│ Your Component │
│ dispatch(action) │
└──────────────┬──────────────┘
│
▼
┌─────────────────────────────┐
│ Store.dispatch │
└──────────────┬──────────────┘
│
▼
┌─────────────────────────────┐
│ Middleware Chain │
│ (logger → thunk → custom..) │
└──────────────┬──────────────┘
│
▼
┌─────────────────────────────┐
│ Reducer │
│ newState = reducer(old, a) │
└──────────────┬──────────────┘
│
▼
┌─────────────────────────────┐
│ Store Updates State │
│ state = newState (new ref)│
└──────────────┬──────────────┘
│
▼
┌─────────────────────────────┐
│ React-Redux Subscriptions │
│ useSelector listeners │
│ compare prev vs next │
└──────────────┬──────────────┘
│
▼
┌─────────────────────────────┐
│ React Re-renders UI │
└─────────────────────────────┘
This is the entire lifecycle of Redux.
🧠 2. Internal Redux store implementation (simplified but accurate)
This is basically what Redux does internally:
function createStore(reducer, enhancer) {
if (enhancer) {
return enhancer(createStore)(reducer);
}
let currentState = reducer(undefined, { type: "@@redux/INIT" });
let listeners = [];
function getState() {
return currentState;
}
function dispatch(action) {
currentState = reducer(currentState, action);
listeners.forEach(listener => listener());
return action;
}
function subscribe(listener) {
listeners.push(listener);
return () => {
listeners = listeners.filter(l => l !== listener);
};
}
return { getState, dispatch, subscribe };
}
This is the TRUE skeleton of Redux.
🔗 3. How combineReducers actually works internally
function combineReducers(reducers) {
return function rootReducer(state = {}, action) {
const nextState = {};
for (let key in reducers) {
const reducer = reducers[key];
nextState[key] = reducer(state[key], action);
}
return nextState;
};
}
It just calls each slice reducer with its own piece of state.
⚙️ 4. How Redux middleware pipeline works (REAL CODE)
Middleware is basically:
dispatch → middleware1 → middleware2 → finalReducer
Actual internal implementation:
function applyMiddleware(...middlewares) {
return function enhancer(createStore) {
return function newCreateStore(reducer) {
const store = createStore(reducer);
let dispatch = store.dispatch;
const middlewareAPI = {
getState: store.getState,
dispatch: (action) => dispatch(action)
};
const chain = middlewares.map(mw => mw(middlewareAPI));
dispatch = compose(...chain)(store.dispatch);
return { ...store, dispatch };
};
};
}
function compose(...funcs) {
return funcs.reduce((a, b) => (...args) => a(b(...args)));
}
This is EXACTLY how applyMiddleware works.
🔌 5. How React-Redux useSelector works internally
function useSelector(selector) {
const store = useReduxContext().store;
const [, forceRender] = useReducer(x => x + 1, 0);
const checkForUpdates = () => {
const newSelected = selector(store.getState());
if (newSelected !== lastSelected) {
lastSelected = newSelected;
forceRender();
}
};
useEffect(() => store.subscribe(checkForUpdates), []);
return selector(store.getState());
}
Meaning:
- Component subscribes to the store.
- If selected value changes → re-render.
🪄 6. How Redux Toolkit createSlice really works (simplified)
RTK uses Immer to allow mutation.
Internally:
function createSlice({ name, initialState, reducers }) {
const actions = {};
const caseReducers = {};
Object.keys(reducers).forEach(key => {
const type = `${name}/${key}`;
actions[key] = (payload) => ({ type, payload });
caseReducers[type] = reducers[key];
});
function reducer(state = initialState, action) {
const caseReducer = caseReducers[action.type];
if (caseReducer) {
return produce(state, draft => {
caseReducer(draft, action);
});
}
return state;
}
return { actions, reducer };
}
Key points:
✔ createSlice auto-generates actions
✔ Reducer is wrapped in Immer → allows mutation (draft)
✔ RTK is just a convenience layer over raw Redux
🚀 Complete Internal Flow (Everything Connected)
Component dispatches an action
│
▼
Middleware (optional)
│
▼
Slice reducer (from createSlice)
│
Immer produces immutable newState
│
▼
Redux store updates reference
│
▼
React-Redux selector checks old vs new
│
▼
If changed → re-render component
thanks GPT