Qwik's core concept is "Resumability," which means the application can seamlessly resume execution state on the client side after server-side rendering without re-executing JavaScript.
Qwik achieves resumability through the following approaches:
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Lazy Loading: Qwik defaults to splitting all JavaScript code into small chunks, loading only necessary code when users interact. This differs from traditional frameworks that typically require downloading the entire application bundle.
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State Serialization: Qwik serializes the application state into HTML. When the page loads, the browser can directly restore the state from HTML without re-executing initialization code.
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No Hydration: Traditional frameworks (like React, Vue) require a hydration process to re-execute JavaScript to attach event listeners. Qwik avoids this step through its unique architecture, directly restoring functionality from HTML.
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Fine-grained Loading: Qwik can load individual functions or components rather than entire modules. This means clicking a button only loads that button's event handler, not the entire application.
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Resumable Execution Context: Qwik maintains an execution context that can be passed between server and client, ensuring code can seamlessly resume in different environments.
The advantages of resumability include:
- Faster First Contentful Paint: No need to download and execute large amounts of JavaScript
- Better Performance: On-demand loading reduces unnecessary code execution
- Better SEO: Server-side rendering provides complete HTML content
- Lower Bandwidth Usage: Only load code that users actually need
Qwik's resumability is implemented through its compiler, which automatically handles code splitting and serialization, so developers don't need to manually manage these details.