How to Implement Lazy Loading for Better Performance

The modern web user values speed and efficiency above many other website characteristics. Lazy loading is a design pattern that defers the loading of non-critical resources at page load time, instead loading them at the moment of need. This can significantly improve performance, especially for pages with many images and scripts. Here we'll explore how to implement lazy loading in web applications, specifically focusing on Astro and React frameworks.

Mon Feb 26 2024

Ben Ajaero

How to Implement Lazy Loading for Better Performance

The modern web user values speed and efficiency above many other website characteristics. Lazy loading is a design pattern that defers the loading of non-critical resources at page load time, instead loading them at the moment of need. This can significantly improve performance, especially for pages with many images and scripts. Here we’ll explore how to implement lazy loading in web applications, specifically focusing on Astro and React frameworks.

What is Lazy Loading?

Lazy loading is a strategy that delays the loading of objects until they are needed, which can reduce initial load times, minimize resource usage, and improve user experience. In the context of web development, it typically refers to images, scripts, or iframes that are only loaded when they enter the viewport or are about to.

Lazy Loading in Astro

Astro is a modern front-end framework that allows developers to build fast websites with less client-side JavaScript. Here’s how you can implement lazy loading in Astro:

Images

Astro offers built-in image optimization with lazy loading. Using the <Image> component from Astro’s @astrojs/image integration, you can easily set up lazy loading:

---
import Image from '@astrojs/image/components/Image.astro';
---

<Image
  src="/path/to/image.jpg"
  alt="Descriptive text for the image"
  loading="lazy"
  width={800}
  height={600}
/>

Scripts

For scripts, you can use dynamic imports combined with the client:visible directive, which loads a component when it comes into view:

---
import { useEffect, useState } from 'react';
---

<div client:visible>
  {() => {
    const [Component, setComponent] = useState(null);
    useEffect(() => {
      import('./HeavyComponent.astro').then(mod => setComponent(mod.default));
    }, []);
    return Component ? <Component /> : <div>Loading...</div>;
  }}
</div>

Lazy Loading in React

React doesn’t have built-in lazy loading for images, but it does support code splitting and lazy loading of components with the React.lazy function and Suspense component.

Images

For images, you can use the loading="lazy" attribute for native lazy loading in browsers that support it:

<img src="path/to/image.jpg" alt="Description" loading="lazy" />

For a more comprehensive solution, you might use a library like react-lazy-load-image-component:

import { LazyLoadImage } from 'react-lazy-load-image-component';

<LazyLoadImage
  src="path/to/image.jpg"
  alt="Description"
  effect="blur"
/>

Components

To lazy load React components, you can use the React.lazy and Suspense:

import React, { Suspense } from 'react';
const LazyComponent = React.lazy(() => import('./LazyComponent'));

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

This will dynamically import LazyComponent only when MyComponent is rendered.

Best Practices

When implementing lazy loading:

• Use placeholders: Display a placeholder or a skeleton screen while the lazy-loaded content is being loaded.
• Consider SEO: Make sure that lazy loading does not hide important content from search engine crawlers.
• Test on slow connections: Ensure that your lazy loading works well even under poor network conditions.

Conclusion

Lazy loading is an excellent technique for improving web performance. By implementing it in Astro or React, you can ensure that your application loads only what’s needed, when it’s needed. This leads to faster page loads, reduced initial page weight, and an overall smoother experience for the user. Remember to keep best practices in mind to handle the loading gracefully and maintain SEO friendliness.

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