Unlock the Power of Lazy Hydration in Vue 3
As web applications continue to grow in complexity and size, performance concerns become a major issue. One way to tackle this is by adopting server-side rendering (SSR) to offload some of the rendering processes from the client. However, even with SSR, site performance can still suffer due to the process of hydration – making the app interactive on the client-side.
The Limitations of Partial Hydration
Partial hydration, where only certain parts of the app are hydrated, is a step in the right direction. This approach is particularly useful when implementing “islands architecture,” where different app sections are considered separate entities. By hydrating only the interactive parts, you can improve performance and user experience.
Enter Lazy Hydration
Lazy hydration takes partial hydration to the next level. Instead of just deciding what parts of the app to hydrate, you can also control when hydration occurs. This allows you to hydrate components only when they’re needed, resulting in significant performance improvements.
Implementing Lazy Hydration in Vue 3
Implementing lazy hydration in Vue 3 is relatively straightforward. You’ll need a wrapper component that renders your component on the server while using conditional rendering on the client-side to delay hydration until certain conditions are met. We’ll explore how to create such a component, inspired by react-lazy-hydration.
Configuring the Lazy Hydration Component
Our lazy hydration component will accept a range of config props, including:
- SSR-only static components
- Hydrating when the browser is idle
- Hydrating when the component is visible
- Hydrating after a Promise resolves
- Hydrating on user interaction
- A callback after the component’s hydrated
Setting Up the Component
We’ll create a setup function to initialize the required values, including a wrapper template ref and a hydrated ref to hold the reactive boolean value. We’ll also create a hydrate function to set the hydrated ref to true.
Handling Hydration
Next, we’ll create an onMounted callback and a watch effect to handle the didHydrate callback. We’ll also set up a primary watch effect to handle the options and set the hydrated ref appropriately.
Visibility-Based Hydration
We’ll use IntersectionObserver to handle visibility-based hydration. If the observer is supported, we’ll initialize it with the provided options. Otherwise, we’ll hydrate immediately.
Browser Idle-Based Hydration
For browser idle-based hydration, we’ll use requestIdleCallback and cancelIdleCallback. If requestIdleCallback is not supported, we’ll implement a fallback with setTimeout.
User Interaction-Based Hydration
Finally, we’ll handle user event-based hydration by looping through events and setting event listeners accordingly.
Using the Lazy Hydration Component
With our lazy hydration component ready, we can test it out in a Vue 3 SSR app. We’ll scaffold a new app using vite-plugin-ssr and set up the lazy hydration component.
Combining Lazy Hydration with Async Components
To further improve performance, we can combine lazy hydration with async components. This will split our app into smaller chunks, ready to be loaded on-demand.
Conclusion
Lazy hydration is a powerful technique for optimizing the performance of Vue 3 apps. By controlling when hydration occurs, you can significantly improve Time to Interactive (TTI) metrics and loading times. With the component implemented in this post, you can take your app’s performance to the next level.