Optimizing Frontend Performance

Prompt Template

"Fynix, I'm optimizing my React application and need help with performance improvements:

1. I have a component [ComponentName] that's large and slows down the initial load time. It's only needed when a user performs a specific action. How can I implement code splitting to load it only when needed?
2. I also have a component [AnotherComponentName] that re-renders unnecessarily. How can I use memoization to prevent this?

Please provide updated code snippets showing how to implement these optimizations.“

Scenario

You have a React application that includes a large component called HeavyComponent, which is only needed when a user performs a specific action (e.g., clicks a button). Currently, HeavyComponent is imported normally, causing it to be included in the initial bundle and slowing down the application's load time.

Additionally, you have a component called ExpensiveList that renders a large list of items. This component re-renders unnecessarily when the parent component updates, even if the items prop hasn't changed, leading to performance issues.

You want to optimize your React application by:

Implementing Code Splitting to load HeavyComponent only when needed. Using Memoization to prevent unnecessary re-renders of ExpensiveList.

Project Structure

my-react-app/
├── src/
│   ├── components/
│   │   ├── HeavyComponent.jsx
│   │   ├── ExpensiveList.jsx
│   │   └── App.jsx
│   └── index.js
└── package.json

Prompt to Use in Fynix

"Fynix, I'm looking to optimize my React application for better performance. Specifically:

1. I have a large component called HeavyComponent that's currently imported like this in App.jsx:

import HeavyComponent from './components/HeavyComponent';

Since HeavyComponent is only needed when the user clicks a button, I want to implement code splitting so it's loaded only when required, reducing the initial bundle size.

2. I also have a component called ExpensiveList that renders a large list of items. It re-renders unnecessarily when the parent component updates, even if the items prop hasn't changed. I want to memoize this component to prevent unnecessary re-renders.

Can you help me achieve these optimizations? Please provide the updated code snippets for @App.jsx and @ExpensiveList.jsx, including any necessary changes or additions. Ensure that the code can be copied and pasted to run immediately.“

Expected Output from Fynix

Updated App.jsx:

// src/components/App.jsx

import React, { useState, Suspense } from 'react';
import ExpensiveList from './ExpensiveList';

const HeavyComponent = React.lazy(() => import('./HeavyComponent'));

function App() {
  const [showHeavyComponent, setShowHeavyComponent] = useState(false);

  const items = Array.from({ length: 1000 }, (_, index) => ({
    id: index,
    name: `Item ${index + 1}`,
  }));

  return (
    <div>
      <h1>Optimized React App</h1>
      <ExpensiveList items={items} />
      <button onClick={() => setShowHeavyComponent(true)}>
        Load Heavy Component
      </button>
      {showHeavyComponent && (
        <Suspense fallback={<div>Loading...</div>}>
          <HeavyComponent />
        </Suspense>
      )}
    </div>
  );
}

export default App;

Updated ExpensiveList.jsx:

// src/components/ExpensiveList.jsx

import React from 'react';

const ExpensiveList = React.memo(({ items }) => {
  console.log('ExpensiveList rendered');
  return (
    <ul>
      {items.map((item) => (
        <li key={item.id}>{item.name}</li>
      ))}
    </ul>
  );
});

export default ExpensiveList;

Instructions to Run and See Output

1. Set Up the React Application If you don't already have a React application set up, create one using create-react-app:

npx create-react-app my-react-appcd my-react-app

2. Create the Component Files

   • Create HeavyComponent.jsx

// src/components/HeavyComponent.jsx
import React from 'react';
function HeavyComponent() {
  return (
    <div>
<h2>Heavy Component Loaded</h2>
<p>This component was loaded dynamically using code splitting.</p>
</div>
  );
}
export default HeavyComponent;

• Create ExpensiveList.jsx Use the updated code provided above.
• Update App.jsx Use the updated code provided above.

3. Run the Application

Start the development server:

npm start

The application will open in your default web browser at http://localhost:3000.

4. ** Test Code Splitting**

   • Initial Load
     • Observe that the application loads quickly.
     • Open the browser's developer tools and go to the Network tab.
     • Refresh the page and note that HeavyComponent is not loaded initially.
   • Load HeavyComponent
     • Click the "Load Heavy Component" button.
     • Observe that the HeavyComponent is displayed.
     • In the Network tab, notice that a new chunk (JS file) is loaded dynamically.

5. Test Memoization

   • Open the Console tab in the developer tools.
   • Observe the log ExpensiveList rendered when the app first loads.
   • Click the "Load Heavy Component" button again.
   • Verify that ExpensiveList does not re-render (no additional logs), confirming that memoization is working.

Note: Replace HeavyComponent, ExpensiveList, and other component names with the actual names used in your project when applying these optimizations.