In which cases should React.memo be used?

React.memo is used to optimize functional components by preventing unnecessary re-renders when props haven't changed.

Use React.memo when:

• The component renders frequently with the same props.
• The rendering of the component is costly in terms of performance.
• The parent component updates often, but the child component should not re-render unnecessarily.

Example:

const MyComponent = React.memo(function MyComponent(props) {
  // component will only re-render if props change
  return <div>{props.value}</div>;
});

It's important to remember that React.memo performs a shallow comparison of props, so for complex objects, a custom comparison function might be needed.