Custom hook
A custom hook is a developer-defined JavaScript function that composes React Hooks to encapsulate reusable stateful or effectful component logic.
React Quickly, Second Edition
A custom hook is a developer-defined function that composes React Hooks to provide reusable component logic.
- How it is used
- Packages component logic for reuse or moves it out of a component to make the UI easier to read.
- How deep it goes
- Defines what qualifies as a custom hook and works through state, context, form, and reducer extractions.
- Examples
- Shows a countdown toggle, form handler, context accessor, counter, and reducer-backed loader; also proposes a timer reset refactor.
- What you can do after
- Build it from scratch to share hook-based logic or simplify a component while preserving the rules of hooks.
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React Hooks in Action: With Suspense and Concurrent Mode
A custom hook is a reusable function that encapsulates React hook logic and can be called by multiple function components.
- How it is used
- Simplifies function components by encapsulating reusable state, context access, subscriptions, side effects, and data fetching.
- How deep it goes
- Explains extraction, composition, parameters, return shapes, cleanup, and Rules of Hooks, while deferring broader centralized data management.
- Examples
- Demonstrates useDocumentTitle, useRandomTitle, useUsers, useFetch, useWindowSize, useUser, and useLocalStorage.
- What you can do after
- Build reusable hooks that extract component logic, compose other hooks, manage effects, and expose focused values or actions.
Read how React Hooks in Action: With Suspense and Concurrent Mode explains custom hook →
React in Depth
A custom hook is a JavaScript function that follows React hook conventions to encapsulate reusable stateful or effectful component logic.
- How it is used
- Uses custom hooks to organize component logic and define focused interfaces between presentation and data layers.
- How deep it goes
- Works through single-hook and composed-hook extractions, application-facing APIs, and a direct test rather than hook internals.
- Examples
- Uses a radio group, user profile, application data API, and keyboard-state test as concrete examples.
- What you can do after
- Build it from scratch by extracting focused component logic, then apply React Testing Library’s renderHook to test a shared hook.
Build AI-Enhanced Web Apps
A reusable React function that composes built-in hooks to encapsulate stateful behavior and related logic.
- How it is used
- Encapsulates chat state management and API submission so React components can concentrate on rendering.
- How deep it goes
- Explains hook structure, state exposure, helpers, side effects, and a concrete submission workflow without covering testing implementation.
- Examples
- Uses ChatPage, ChatList, messages, loading feedback, and the useChatFormSubmit chat-submission hook.
- What you can do after
- Apply it via React to isolate reusable stateful behavior and keep component logic maintainable.
Related concepts
- React hookuses · A React Hook is a function-based API that enables function components to access state, effects, context, and other React capabilities.
- rules of hooksconfigured by · The Rules of Hooks are React constraints requiring Hooks to be called at the top level of function components or custom Hooks, unconditionally and in consistent order.
- function componentused by · A function component is a user-interface component implemented as a function that receives inputs and returns a description of its rendered content.
- frontend developmentused by · Frontend development is the practice of building the user-facing, client-side interfaces and behavior through which people interact with software.
- callbackkind of · A callback is a function or other callable supplied to software for invocation later in response to a specified event, condition, or point in execution.
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