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Boosting Your React App's Performance with React.lazy and Suspense

In today's fast-paced world, users expect web applications to load quickly and perform optimally. This applies to React applications as well. One way to optimize your React app's performance is by dynamically loading components using a technique called code splitting. Code splitting allows you to break your app into smaller chunks and load only the necessary parts, making it faster and more efficient.

In this post, we'll explore how to use React.lazy and Suspense to implement code splitting in your React application and boost its performance.

What is Code Splitting?

Code splitting is a technique where you break your app into smaller chunks (or modules) and load only the necessary parts when needed. By doing this, you can reduce the size of your initial bundle, making it faster to load.

A good example of where code splitting comes in handy is with a web application that has a large, complex UI. In this case, the initial bundle may take a long time to load, causing the user to experience a slow-loading application. By splitting the code into smaller chunks, you can load only the components that are needed for the initial view and defer the rest until needed, reducing the initial load time.

What is React.lazy?

React.lazy is a function that allows you to load React components lazily (aka on-demand) when they are needed. This function makes it easy to implement code splitting in your React application.

To use React.lazy, you simply create a placeholder component that will be used for rendering the lazy-loaded component. This placeholder component will render a loading indicator while the lazy-loaded component is being loaded.

import React, { lazy, Suspense } from 'react';

// create a lazy loaded component
const MyComponent = lazy(() => import('./MyComponent'));

function App() {
  return (
    <div>
      <Suspense fallback={<div>Loading...</div>}>
        <MyComponent />
      </Suspense>
    </div>
  );
}

In this example, we import MyComponent using the lazy function and pass in a function that returns the import. We then wrap the MyComponent component inside a Suspense component which will render a fallback component (in this case 'Loading...') while the component loads.

What is Suspense?

Suspense is a new feature in React 16.6 that allows you to wait for a component to load asynchronously. This can be used for lazy-loading components, data fetching, or any other async operation.

Using Suspense, you can wrap a component that is loading asynchronously with a fallback component that will be displayed while the component is being loaded.

Combining React.lazy and Suspense

Using React.lazy and Suspense together allows you to lazily load components and asynchronously wait for them to load. When used properly, this can have a big impact on your app's performance and user experience.

Here is an example of how you can use React.lazy and Suspense together:

import React, { lazy, Suspense } from 'react';

const MyComponent = lazy(() => import('./MyComponent'));

function App() {
  return (
    <div>
      <Suspense fallback={<div>Loading...</div>}>
        <MyComponent />
      </Suspense>
    </div>
  );
}

In this example, we lazily load the MyComponent component asynchronously and wrap it inside a Suspense component. We also provide a fallback component that will be displayed while MyComponent is being loaded.

Conclusion

In this post, we explored how to use React.lazy and Suspense to dynamically load components and implement code splitting in your React application. By breaking your app into smaller chunks and loading only the necessary parts when needed, you can optimize your app's performance and provide a better user experience. By implementing code splitting with React.lazy and Suspense, you can ensure that your app is fast and efficient, even as it grows in complexity.