Instruction: Describe what memoization is and how it can be applied in a React application to optimize performance.
Context: This question assesses the candidate's understanding of optimization techniques in React, specifically memoization, to prevent unnecessary re-renders.
Official answer available
Preview the opening of the answer, then unlock the full walkthrough.
To clarify, memoization in React doesn't refer to general JavaScript memoization of any function's output based on its inputs. Instead, it specifically applies to React components and their render output. When React props or state change, React re-renders the component to update the UI. However, if the props or state that affect the component's output haven't changed, re-rendering is unnecessary and can be a waste of resources. That's where memoization comes in.
React provides a higher-order component named React.memo for this purpose. React.memo wraps around a functional component. It shallowly compares the previous and current props. If they are the same, React skips rendering the component and reuses the last rendered result, thus saving...