DEV Community

Cover image for The Architecture of the Reactivity Layer in Solid.js
Maciej Kwaśniak
Maciej Kwaśniak

Posted on

The Architecture of the Reactivity Layer in Solid.js

One of the key features of solid.js is its reactivity layer, which allows web applications built with solid.js to automatically update in response to changes in the data. This makes it easy to build interactive and dynamic web applications without having to manually update the user interface.

In this article, we will explore the architecture of the reactivity layer in solid.js and how it works to enable reactive programming in web applications.

The reactivity layer in solid.js is based on a set of core principles and concepts, including observables, observers, and reactive functions.

Observables are objects that represent the state of a web application and can be observed by other components. For example, an observable could be a variable that stores the current value of a form input, or a data collection that holds a list of items. Observables are designed to be easy to use and flexible, so they can be used to represent a wide range of data types and structures.

Observers are components that subscribe to observables and receive notifications when the observables change. Observers can be functions, components, or other objects that are interested in the state of an observable. When an observable changes, the observer is notified and can react to the change by updating the user interface or performing other actions.

Reactive functions are the core building blocks of the reactivity layer in solid.js. These are special functions that take observables as inputs and return values that are derived from the observables. When the observables change, the reactive functions automatically update to reflect the new values of the observables.

For example, a reactive function could be used to calculate the total price of a shopping cart, based on the prices and quantities of the items in the cart. If the prices or quantities of the items change, the reactive function will automatically update the total price to reflect the changes.

In solid.js, reactive functions are implemented using a technique called "computation expression", which allows reactive functions to be written in a declarative and concise manner. This makes it easy to write complex reactive functions without having to worry about the details of how the reactive logic is implemented.

The architecture of the reactivity layer in solid.js is designed to be scalable, efficient, and easy to use. It uses a set of algorithms and data structures that are optimized for reactive programming, so that web applications built with solid.js can handle a large number of observables and reactive functions without slowing down.

Overall, the reactivity layer in solid.js is a key component of the library that enables developers to build interactive and dynamic web applications. By leveraging the power of reactive programming, solid.js makes it easy to build web applications that are responsive, flexible, and easy to maintain.

This article was written by Assistant, a large language model trained by OpenAI. It is published under the Creative Commons Attribution 4.0 International (CC BY 4.0) license.

Top comments (2)

lexlohr profile image
Alex Lohr

Not too bad, but the depth of understanding is obviously lacking.

For the sake of this explanation, consider memos computed values derived from other state and effects computations without an exposed value.

In Solid, JSX is automatically rewritten into templates and effects manipulating the DOM (at least in the client, SSR is a different story). There are a few special cases, e.g. events are only bound once.

One of the most important things missing in the explanation is the concept of dependency tracking, which is done automatically through access within the scope of a tracking function, also called the root of solid's reactivity. Every evaluation of an observable inside this scope subscribes the current computation (memos and effects) to changes of that observable, so any time the observable is changed, the array of subscribed computations is re-evaluated. On disposal, all subscriptions are cleared and can be garbage-collected.

The observables are exposed to the developer as JSX, signals, resources (asynchronous signals) stores and mutables.

exelord profile image
Maciej Kwaśniak

Yes, thanks. That's more in-depth take. But overall I think the assistant did an amazing job explaining the top level view on the topic :)

16 Libraries You Should Know as a React Developer

Being a modern React developer is not about knowing just React itself. To stay competitive, it is highly recommended to explore the whole ecosystem. This article contains some of the most useful React component libraries to speed up your developer workflow.