Astro: A Fast and Flexible Framework for Building Web Applications
Key Features of Astro
Astro provides several features that make it an ideal choice for building fast and scalable web applications.
- Partial Hydration: Astro allows developers to hydrate only the necessary parts of the application, reducing the amount of JavaScript code that needs to be shipped.
- Islands Architecture: Astro uses an islands architecture, which means that each component is rendered independently, allowing for better performance and caching.
- UI-Agnostic: Astro is UI-agnostic, meaning that you can use any UI framework (such as React, Preact, Solid, Svelte, Vue, and Lit) or even mix and match different frameworks on the same page.
How Astro Works
Astro achieves its features through its unique architecture and rendering process. Here’s a high-level overview of how Astro works:
- Server-Side Rendering: Astro renders your application on the server, generating HTML and CSS.
- Client-Side Hydration: Astro hydrates the necessary parts of your application on the client-side, using partial hydration.
- Islands Rendering: Astro renders each component independently, using an islands architecture.
// Example of Astro's server-side rendering
import { render } from '@astrojs/core';
const html = render('/path/to/page');
console.log(html); // Output: <html>...</html>
Client Directives
Astro provides several client directives that allow you to control how your components are rendered and hydrated. These directives include:
- client:load: Hydrates the component JavaScript immediately on page load.
- client:idle: Hydrates the component JavaScript once the page is done with its initial load and the requestIdleCallback event has fired.
- client:visible: Hydrates the component JavaScript once the component has entered the user’s viewport.
- client:media={string}: Hydrates the component JavaScript once a certain CSS media query is met.
- client:only={string}: Skips HTML server rendering and renders only on the client.
<div client:visible>
<p>This content will be hydrated when the component is visible</p>
</div>