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Understanding Re-rendering in React

React is known for its efficient rendering engine that optimizes updates to the DOM, keeping UI interactions fast and responsive. But understanding how and when React triggers re-renders, especially when passing elements as props or children, is key to building performant applications. This blog post will dive into the mechanisms behind React's re-rendering process, discuss how elements passed as props or children can impact re-renders, and explore how React uses Object.is for re-render checks.
React uses Object.is to compare the new and previous values of state and props. If Object.is returns false, React checks whether the component's type is the same before deciding to re-render. For children components, React does not automatically re-render unless their props or context change.

Managing Re-Renders

Here are some key strategies to minimize unnecessary re-renders:

  1. Memoize Components with React.memo: This prevents functional components from re-rendering unless their props have changed.
  2. Use useCallback and useMemo: Memoize functions and values to maintain stable references and prevent triggering re-renders in child components.
  3. Avoid Inline Functions and Objects in JSX: These create new references every render, causing unnecessary re-renders when passed as props.
  4. Passing Elements as Props: Passing JSX elements as props can lead to re-renders because React treats them as unique instances. Instead, use configuration data or wrap components with React.memo.