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Ishan Bagchi
Ishan Bagchi

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Exploring React Lazy with Suspense: Code-Splitting Made Easy

In modern web development, performance optimization is crucial to provide a smooth user experience. One of the ways to achieve this is by code-splitting, which allows us to load only the necessary code when it's needed. React Lazy with Suspense is a powerful feature that simplifies code-splitting in React applications. In this blog post, we will dive into the world of React Lazy with Suspense, explore its benefits, and understand how to implement it using code examples.

What is Code-Splitting?

Code-splitting is a technique that involves breaking down a large JavaScript bundle into smaller, more manageable chunks. By splitting the code, we can load only the required portions of the application when they are needed, reducing the initial loading time. This technique is especially useful for large-scale applications with complex components.

Introducing React Lazy with Suspense:

React Lazy with Suspense is a combination of two features introduced in React 16.6.0. React Lazy allows us to render a dynamic import as a regular component, while Suspense handles the fallback UI while the dynamically imported component is being loaded. This powerful duo simplifies the process of code-splitting and lazy loading in React applications.

Using React Lazy with Suspense:

To demonstrate the usage of React Lazy with Suspense, let's consider a scenario where we have a large component called ExpensiveComponent that we want to lazy load.

Step 1: Import the necessary modules:

import React, { lazy, Suspense } from 'react';
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Step 2: Define the lazy-loaded component:

const ExpensiveComponent = lazy(() => import('./ExpensiveComponent'));
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Step 3: Wrap the lazy-loaded component with Suspense and provide a fallback UI:

function App() {
  return (
      <h1>Welcome to My React App</h1>
      <Suspense fallback={<div>Loading...</div>}>
        <ExpensiveComponent />
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In the above example, when ExpensiveComponent is rendered, React will automatically load the component asynchronously. While the component is being loaded, the fallback UI (in this case, the "Loading..." text) will be displayed. Once the component is loaded, it will be rendered in place of the fallback UI.

Benefits of React Lazy with Suspense:

  1. Improved Performance: Code-splitting helps reduce the initial bundle size, resulting in faster loading times for your application.
  2. Better User Experience: By displaying a fallback UI, Suspense ensures that users are aware that content is loading, improving the overall experience.
  3. Simplified Implementation: React Lazy with Suspense provides an easy-to-use API that abstracts away the complexities of lazy loading and code-splitting.

Considerations and Limitations:

While React Lazy with Suspense is a powerful tool, there are a few considerations and limitations to keep in mind:

  • Suspense can only be used with React components that are lazy-loaded using React Lazy.
  • Suspense currently only supports fallback UI at the component level, not for specific portions of a component.
  • The fallback UI must be a React element or a component. It can be as simple as a loading spinner or as complex as a custom component.


React Lazy with Suspense is an excellent addition to the React ecosystem, enabling developers to easily implement code-splitting and lazy loading in their applications. By splitting code into smaller, more manageable chunks and displaying fallback UI during loading, we can significantly improve performance and enhance the user experience. Remember to use React Lazy with Suspense strategically to achieve the best results and deliver high-performing React applications.

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