Class component
A class component is a user-interface component implemented as a class that defines or supplies its state, behavior, rendering, or lifecycle.
React Quickly, Second Edition
A class-based component is a React component defined as a JavaScript class with rendering and lifecycle behavior.
- How it is used
- Replaces repeated UI elements with reusable components and supports stateful interfaces.
- How deep it goes
- Works through rendering and class state, but defers error-boundary method details.
- Examples
- Uses three repeated links and a click counter to demonstrate rendering, reuse, and updates.
- What you can do after
- Build it from scratch: define a reusable class component, render JSX, and update a counter with this.setState.
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React Hooks in Action: With Suspense and Concurrent Mode
A class component is a React component defined as a JavaScript class extending React's component base or compatible class behavior.
- How it is used
- Uses classes for stateful components, side effects, DOM work, or direct event responses.
- How deep it goes
- Defines constructors, lifecycle methods, and render, but defers detailed lifecycle mechanics to comparison with Hooks.
- Examples
- Shows a class listing with constructor state, componentDidMount data loading, and render-generated UI.
- What you can do after
- Build it from scratch as a stateful React component with constructor state, lifecycle side effects, and render-based UI.
Read how React Hooks in Action: With Suspense and Concurrent Mode explains class component →
Related concepts
- React hookcontrasts with · A React Hook is a function-based API that enables function components to access state, effects, context, and other React capabilities.
- error boundaryused by · An error boundary is a React component mechanism that catches errors in descendant components and renders fallback UI to isolate the affected component tree.
- componentuses · A software component is a modular part of a larger system that provides related functionality and interacts with other parts through defined boundaries or interfaces.
- initializeruses · An initializer is a function, declaration, or language construct that establishes the initial value or state of an object, value, computation, or process.
- statehas part · State is information or a configuration describing the condition of a system, entity, or computation at a particular time and potentially influencing subsequent behavior or decisions.
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