When you build large web applications with React, your app can become slow. This happens because all the code is loaded at once, even if the user only needs a small part of it at the beginning. To solve this, developers use a method called code-splitting.
The most common form of code-splitting is lazy loading. It loads parts of the app only when they are needed. For example, if a user visits the homepage, the code for the settings page is not loaded until they go there. This saves time and improves speed.
But lazy loading is just the beginning. There are more advanced ways to split your React code and make your app faster and smarter. These extra strategies are very helpful for big applications. That’s why they are often included in modern full stack developer classes, where students learn how to improve performance using smart tools and designs.
In this blog, we will explore other useful code-splitting methods beyond lazy loading.
Why Code-Splitting Matters
Before jumping into the strategies, let’s understand why code-splitting is important.
Imagine your app is like a big backpack. If you carry everything at once, it becomes heavy and slow. But if you take only what you need at the right time, it’s easier to move.
With code-splitting, the browser downloads only the code it needs. This gives users:
- Faster first load time
- Less waiting
- Better experience on slow networks
- Lower chance of crashes on small devices
Let’s now look at different ways to split your code smartly.
Dynamic Imports (Beyond Lazy)
React’s React.lazy() is a simple way to do lazy loading. But you can use dynamic imports with custom logic.
For example:
if (userIsAdmin) {
import(‘./AdminDashboard’).then((module) => {
const AdminDashboard = module.default;
render(<AdminDashboard />);
});
}
This lets you load code based on user roles, settings, or actions. You can control when and how to load each part.
Use cases:
- Admin pages only loaded for admins
- Language files loaded based on user choice
- Large charts only loaded when visible
Route-Based Splitting with React Router
One of the best ways to split code is by routes. Each page or screen gets its own bundle.
Using React.lazy() with React Router:
const Home = React.lazy(() => import(‘./Home’));
const About = React.lazy(() => import(‘./About’));
<Routes>
<Route path=”/” element={<Home />} />
<Route path=”/about” element={<About />} />
</Routes>
This method ensures that each route loads only when visited. For big apps with many pages, this keeps the initial load very small.
Component-Level Splitting
Sometimes even a single page has large components. You can split those too.
Example:
- A dashboard page may have graphs, tables, and lists.
- Load only the main part first, and then load the graphs later.
const Graph = React.lazy(() => import(‘./Graph’));
function Dashboard() {
return (
<div>
<MainInfo />
<Suspense fallback={<Loading />}>
<Graph />
</Suspense>
</div>
);
}
This method helps make even big pages load faster in parts.
Library Splitting
Modern apps use many libraries like lodash, moment.js, or chart libraries. These can be large.
Strategy: Import only what you need.
Instead of:
import _ from ‘lodash’;
Do this:
import debounce from ‘lodash/debounce’;
This reduces the bundle size by avoiding the full library. Tools like Webpack Tree Shaking also help remove unused code automatically.
Learning how to handle third-party libraries properly is part of every smart full stack course because these skills directly affect performance.
Bundle Splitting with Webpack
Webpack allows you to split bundles into smaller chunks using its config file.
You can create:
- Vendor chunk: For third-party libraries
- App chunk: For your own app code
- Runtime chunk: For Webpack-related code
This lets browsers cache the vendor chunk separately. So, when you update your app, users don’t have to download the libraries again.
Webpack config example:
optimization: {
splitChunks: {
chunks: ‘all’,
},
},
This is helpful when your app grows and you want to reuse common parts like headers, footers, or shared styles.
Predictive Prefetching
Another smart idea is prefetching. It means loading code in advance before the user asks for it.
Use it for parts that the user is likely to visit next.
<link rel=”prefetch” href=”about.js” />
You can also use React.lazy() with a custom prefetch function:
const About = React.lazy(() =>
import(/* webpackPrefetch: true */ ‘./About’)
);
This makes the browser download the file quietly in the background. When the user visits the page, it opens instantly.
Use cases:
- Prefetch dashboard after login
- Prefetch checkout page after adding to cart
Parallel Loading and Streaming
In React 18, there is a new feature called streaming server-side rendering (SSR). It allows your app to send parts of HTML to the browser as soon as they are ready.
This works well with code-splitting. Your app can show the header and nav first, then send the main content later.
Streaming and parallel loading are great for news sites, blogs, and product pages.
Code-Splitting in Micro Frontends
Some large teams use micro frontends breaking the app into small independent parts owned by different teams.
Each part can use its own code-splitting. For example:
- Team A owns /profile
- Team B owns /checkout
Each team builds and deploys its part with lazy loading and route-based splitting.
Together, the full app works faster and allows teams to work separately.
Tools That Help with Code-Splitting
Here are some helpful tools and libraries:
- Webpack – Most popular bundler
- Vite – Fast modern alternative to Webpack
- React.lazy and Suspense – Easy lazy loading
- Loadable Components – Advanced loading control
- Bundle Analyzer – See what’s in your bundles
- React Router – Route-based code splitting
Using these tools is often included in exercises and projects during full stack developer classes because they help students build real apps that perform well in the real world.
Common Mistakes to Avoid
While code-splitting is great, it can cause problems if not done right.
1. Splitting Too Much
If you split every small component, the app might make too many requests. This slows down the app.
Tip: Split only big or rarely-used components.
2. No Fallback UI
Always show a loading spinner or message when a part is being loaded.
<Suspense fallback={<div>Loading…</div>}>
<LazyComponent />
</Suspense>
3. Not Testing on Slow Networks
Always test your app on a slow internet connection. This shows you how the app behaves when loading parts.
Final Thoughts
Code-splitting helps make React apps faster and smarter. While lazy loading is a good start, there are many more ways to improve your app:
- Use dynamic imports with conditions
- Split by routes, components, or libraries
- Prefetch likely pages
- Use Webpack or Vite for advanced splitting
- Monitor with bundle tools
If you’re learning React or full stack development, try using these methods in your next project. You don’t need to apply all at once. Start simple, then improve as your app grows.
Understanding and using these strategies is an important skill taught in every full stack course because it helps developers build apps that are not only functional but also fast and efficient.
So next time you build with React, remember loading less is more. Code-splitting is your secret weapon to keep your app quick, light, and ready for users.
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