React.memo

What this means

React.memo can let a component skip rendering if its props have not changed. It is useful for expensive child components with stable props.

In beginner terms, this topic answers one practical question: "What should I write, and why does React care about it?" Do not try to memorize the syntax first. First understand the idea, then connect the syntax to that idea.

Why it matters

Memoization can help, but it has a cost. If props always change, React.memo will not help much.

When you build real React screens, this idea helps you decide where data should live, what the user should see, and what should happen after an interaction. That is why this lesson is part of the main path instead of being an optional detail.

Step by step

1. Notice the UI problem this topic solves. 2. Look at the smallest possible example. 3. Change one value and predict what should appear. 4. Run the example and compare the result with your prediction. 5. Use the practice task before moving on.

Small example

const Row = React.memo(function Row({ item }) {
  return <li>{item.name}</li>;
});

Common mistake

Do not wrap every component in React.memo. It can make code noisy without improving performance.

Practice task

Identify one component in a list that might benefit from memoization if rendering becomes expensive.

Remember this

Memoization should be targeted.