Why React.memo and useMemo in React Native? - Purpose & Use Cases

The Big Idea

What if your app could skip boring repeated work and run lightning fast without extra effort?

The Scenario

Imagine you have a mobile app with many components that update often. Each time you change something, the whole screen refreshes, even parts that didn't change.

This makes the app slow and laggy, like repainting your whole room when you only want to change one picture.

The Problem

Without smart tools, your app wastes time redoing work it doesn't need to do. This slows down the app and drains battery.

It's like rewriting a whole essay every time you fix one typo -- tiring and inefficient.

The Solution

React.memo and useMemo help your app remember parts that didn't change. They skip redoing work for those parts, making your app faster and smoother.

It's like putting sticky notes on your work to remind you what's done, so you only focus on what really needs fixing.

Before vs After

✗ Before

function MyComponent(props) {
  return <Text>{props.value}</Text>;
}
// Re-renders every time parent updates

✓ After

const MyComponent = React.memo(function MyComponent(props) {
  return <Text>{props.value}</Text>;
});
// Skips re-render if props.value is same

What It Enables

It enables building fast, smooth apps that feel responsive and save battery by avoiding unnecessary work.

Real Life Example

In a chat app, React.memo prevents message bubbles from re-rendering when you type a new message, so scrolling stays smooth.

Key Takeaways

Manual re-rendering slows apps and wastes resources.

React.memo and useMemo remember unchanged parts to skip work.

This leads to faster, smoother, and more efficient apps.