Beyond Signals: The Next Big Shift in Web Reactivity

Ryan Carniato is the author of SolidJS, a JavaScript library for building user interfaces.

Signals are primitives used for representing synchronization in front-end frameworks, ensuring that changes in state automatically update dependent computations without reassigning variables.

SolidJS uses signals as a core part of its reactivity model, which allows fine-grained updates without re-running entire components, unlike traditional frameworks that rely on virtual DOM updates.

React has not adopted signals at its core because its re-render model focuses on re-running components, which is philosophically different from the signal-based approach where only specific parts are updated.

Fine-grained rendering allows updates to be localized only to the parts of the UI that depend on the changed data, improving performance by avoiding unnecessary re-renders of components.

SolidJS uses derived async signals to manage asynchronous operations, allowing for parallel data fetching and eliminating client-side waterfalls, which ensures updates occur seamlessly without blocking UI rendering.

Projections in SolidJS are a new primitive that allow for creating derived and granular reactive data, enabling the extension or splitting of reactivity without altering the original data source.

SolidJS flattens the component tree by deferring prop reads to the necessary points, unlike React's context which can cause re-renders down the component hierarchy.

SolidJS embraces controlled mutability for stable references and performance, allowing for granular updates without unnecessary re-renders, contrasting with the immutability favored in functional programming.

Ryan Carniato anticipates further evolution in SolidJS's handling of reactive data graphs, async operations, and expanding the library's functionality with new primitives and features.