serializableCheck
React chapter 86 · RTK · serializableCheck · source: reduxjs/redux-toolkit/packages/toolkit/src/serializableStateInvariantMiddleware.ts
The problem
A form puts a File or a Date class into Redux. DevTools time-travel JSON-replays the log: Date becomes a string, File becomes {}, class methods vanish. Persist/rehydrate is the same bug. Functions in state never belong there.
The pattern that fixes it
Default middleware rejects non-plain values in actions and state (Date, Map, Set, File, class instances, functions). Store ISO strings and ids. Keep File in component state or FormData (chapter 73).
Keep learning
- Previous: combineSlices / inject
- Next: createApi + fetchBaseQuery
- Related: configureStore
- Related: createAction
- Related: extraReducers + matchers
- Related: createEntityAdapter
- Related: createSelector
- Related: createListenerMiddleware
More courses
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- Match a job post to courses — Paste a job post. Each skill is matched to a track here and put in learning order, foundations first.
- Database in depth — How a query becomes work. Indexes, isolation, locks, and the plans that explain why a page is slow — not an ORM tour.
- System Design — Eight interview case studies, from a flash sale and Tatkal to a live final and a chat model, plus JWT in separate chapters.
- Microservices — Microservice patterns one diagram at a time: how to split a monolith, how services talk, and how data stays consistent without distributed transactions.
- Kafka — A beginner-to-senior path through event logs, reliable delivery, production operations, and disaster recovery.
- Frontend system design — How a UI is sliced when it is a product, not a page: ownership of state, cache, routes, and what happens when the network lies.
- CSS in depth — See the box, then the page. Visual chapters from the box model through Flexbox surprises, Grid, selectors, and units, then backgrounds, shapes, and visual effects, each with a playground.
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