Redux & Redux Toolkit Course
Redux & Redux Toolkit
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Intermediate

Avoid Unnecessary Re-renders

Definition

The goal of ensuring that a React component connected to Redux only updates the DOM when the specific piece of state it relies on has been modified.

Explain Like I'm New

If a user typing in an email input field causes the entire Navbar, Sidebar, and Footer to re-render, your app will feel laggy and terrible. You must architect your selectors so components ignore state changes they don't care about.

Real World Example

If your `UserProfile` component selects `state.user`, it should NOT re-render when `state.cart` updates.

Common Use Cases

  • •Optimizing React performance
  • •Large scale application architecture

Interactive Example

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Interview Questions

basic

  • Should you put everything into one massive `useSelector` or split them up into multiple `useSelector` calls?

intermediate

  • If a parent component re-renders, do its children re-render even if their `useSelector` data didn't change?

Flash Cards

Question

One massive or multiple?

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Answer

Split them up! Calling `useSelector` 5 times for 5 specific strings is vastly better than calling `useSelector` once to return a massive object, because returning an object forces a re-render every time.

Question

Do children re-render?

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Answer

Yes! This is a core React rule. If a Parent re-renders, all Children re-render by default, completely bypassing `useSelector` optimizations. You must wrap the Children in `React.memo()` to stop this.