Server-Side Rendering (SSR) has become a popular technique to improve performance and SEO for web applications. One important aspect of SSR is hydration, which ensures that the client-side JavaScript code seamlessly takes over the rendered HTML and continues to enhance the user experience.

When using dynamic imports in JavaScript, there are a few considerations to keep in mind to handle SSR hydration correctly. This article will explore how to handle SSR hydration with dynamic imports effectively.

What are Dynamic Imports?

Dynamic imports allow you to asynchronously load JavaScript modules when they are needed, rather than including them in the initial bundle. This helps improve website performance, as only the necessary modules are loaded when required.

Dynamic imports are especially useful when implementing code-splitting, where different parts of the application are split into separate bundles and loaded on-demand. This reduces the initial load time, as only essential resources are fetched first.

The Challenge with SSR Hydration and Dynamic Imports

When rendering a web page on the server-side, the dynamic imports are not executed, as there is no client-side JavaScript running. This means that any component or functionality dynamically imported will not be available in the initial HTML that is sent to the client.

To handle SSR hydration correctly, you need to ensure that any dynamically imported components or functionality are properly loaded and executed on the client-side.

Solution: Loadable Components

A popular library for handling SSR hydration with dynamic imports is “Loadable Components”. This library provides a declarative way to load modules on both server and client-sides.

Here’s a step-by-step guide to implementing SSR hydration with dynamic imports using Loadable Components:

1. Install the @loadable/component package via npm or yarn.

npm install @loadable/component

1. Import the Loadable function from @loadable/component and use it to load your dynamic import:

import { Loadable } from '@loadable/component'

const MyComponent = Loadable(() => import('./MyComponent'))

1. On the server-side, use the Loadable.preloadAll method to preload all the dynamic imports before rendering the HTML:

import { preloadAll } from '@loadable/component'

// Call the preloadAll function to load all dynamic imports
await preloadAll()

1. Server-side rendering your application and include the serialized state of the dynamic imports in the rendered HTML.

2. On the client-side, use the Loadable function to render the dynamic imports, passing the serialized state as a prop:

import { hydrate } from 'react-dom'
import { LoadableCapture } from '@loadable/component'

// Hydrate the dynamic imports using the serialized state
hydrate(
  <LoadableCapture report={m => modules.push(m)}>
    <App />
  </LoadableCapture>,
  document.getElementById('root')
)

Conclusion

Handling SSR hydration with dynamic imports is essential to ensure that your web application functions correctly and delivers an optimal user experience. By using libraries like Loadable Components, you can effectively manage the loading and rendering of dynamically imported modules on both server and client-sides.

Remember to preload the dynamic imports on the server-side and serialize their state for hydration on the client-side. This way, your web application will seamlessly transition from server-rendered HTML to client-side rendered components.

#references

• Loadable Components Documentation
• Dynamic Imports in JavaScript
• Server-Side Rendering in React