react/React APIs

React.memo skips re-rendering a component if its props are shallow-equal to the previous render's — the function-component equivalent of PureComponent. Suspense lets part of a component tree 'wait' for something (most commonly lazily-loaded code, or data via the right integration) and show a fallback while it's not ready, and React.lazy pairs with it to code-split a component so its code only loads once it's actually about to render.

forwardRef lets a component explicitly accept a ref and forward it to a child DOM node or component, since refs aren't passed like normal props by default. Fragment lets you group multiple children without introducing an extra wrapper node into the actual DOM. cloneElement and the Children utilities let you inspect or transform the children passed into a component, though they're reached for far less often now that hooks and composition patterns cover most of the same problems more predictably.