Rerender

Rerender is the process by which a user interface component regenerates its visual output in response to changes in data or state. In client-side rendering, a rerender typically occurs after an update to a component’s state, properties, or context, and is distinct from the initial render that occurs when a component is mounted. The goal of a rerender is to reflect the latest data while preserving as much of the existing DOM as possible.

In modern front-end frameworks, rerendering is coordinated through a reconciliation process. For example, in React a rerender is triggered when state is updated or a component receives new props. The framework constructs a virtual representation of the UI, compares it with the previous version, and applies only the necessary changes to the actual DOM. This selective update minimizes direct DOM operations and helps maintain responsive interfaces.

Performance considerations are central to rerendering. Frequent or unnecessary rerenders can degrade performance, especially in large component trees. Techniques to control rerendering include memoization and limiting updates: wrapping functional components with memory helpers (such as higher-order components that prevent rerendering when props are unchanged), using shouldComponentUpdate or PureComponent in class-based components, and employing useMemo and useCallback to stabilize dependencies. Additionally, avoiding the creation of new objects or functions during render and splitting state so that only affected parts rerender can improve efficiency.

Different frameworks implement rerendering with varying mechanisms. Vue uses a reactive data model to trigger rerenders when dependencies change, Angular employs change detection strategies, and Svelte compiles away updates to minimize runtime work. Across ecosystems, rerender remains the core mechanism by which UIs stay in sync with changing data.