Angular 18 introduces Partial Hydration, a powerful technique that significantly improves application performance in conjunction with Server-Side Rendering (SSR). This article dives into the concept of partial hydration, its benefits, and how it leverages deferrable views introduced in Angular 17.
According to Angular Roadmap:
Weβre already seeing significant improvements to Core Web Vitals, including LCP and CLS. In lab tests, we consistently observed 45% better LCP of a real-world app.
Why Partial Hydration and SSR Matter
Traditional Angular applications often suffer from a performance bottleneck when loading all JavaScript upfront. This can significantly impact the initial load time, especially for large and performance-critical applications. By strategically reducing the amount of JavaScript loaded at the start, we can drastically enhance user experience.
Partial Hydration: A Smarter Approach to SSR
Partial hydration builds upon the foundation of deferrable views, introduced in Angular 17. Instead of rendering a simple placeholder on the server, Angular can now render the main content of a designated block marked with @defer. Here's how it works:
- Server-side Rendering: The server renders the essential content of the application along with the @defer block containing the component.
- Client-side Hydration: When the application runs on the client, Angular downloads the necessary JavaScript for the deferred component.
- Selective Activation: The deferred component only becomes interactive when it meets specific conditions, like entering the user's viewport.
This approach offers several advantages:
- Faster Initial Load Times: By deferring unnecessary JavaScript, users experience a quicker initial page load.
- Improved Perception: The application feels more responsive as core functionalities are available instantly.
- Reduced Data Consumption: Smaller initial JavaScript payloads translate to lower data usage.
Enabling Partial Hydration
Utilizing partial hydration is straightforward. Here's an example:
{
@defer (render on server; on viewport) {
<my-deferrable-component></my-deferrable-component>
}
}
In this example:
-
my-deferrable-component
is rendered on the server. - Client-side, Angular downloads the required JavaScript for the component.
- Interaction with
my-deferrable-component
only occurs when it enters the viewport, optimizing rendering and performance.
Conclusion
Partial hydration empowers Angular developers to create performant and user-friendly applications. By strategically deferring component hydration based on user interaction or visibility, Angular 18 ensures a smooth and responsive user experience, especially for complex and data-heavy applications.
Top comments (1)
doesnt work, there is no such trigger as render on server?