solid-js

What is solid-js?

Solid.js is a declarative JavaScript library for building user interfaces. It focuses on fine-grained reactivity, which allows for highly efficient updates and minimal re-renders. Solid.js is designed to be fast and simple, providing a reactive programming model that is easy to understand and use.

What are solid-js's main functionalities?

Reactive State Management

Solid.js uses fine-grained reactivity for state management. The `createSignal` function creates a reactive state that updates the UI efficiently when the state changes.

import { createSignal } from 'solid-js';

function Counter() {
  const [count, setCount] = createSignal(0);
  return (
    <div>
      <button onClick={() => setCount(count() + 1)}>Increment</button>
      <p>Count: {count()}</p>
    </div>
  );
}

JSX Support

Solid.js supports JSX, allowing you to write HTML-like syntax within JavaScript. This makes it easy to create and manage UI components.

import { render } from 'solid-js/web';

function App() {
  return (
    <div>
      <h1>Hello, Solid.js!</h1>
    </div>
  );
}

render(() => <App />, document.getElementById('root'));

Component Composition

Solid.js allows for easy component composition. You can create reusable components and pass data to them via props.

function Greeting(props) {
  return <h1>Hello, {props.name}!</h1>;
}

function App() {
  return (
    <div>
      <Greeting name="Solid.js" />
    </div>
  );
}

Direct DOM Manipulation

Solid.js provides direct DOM manipulation capabilities. The `onCleanup` function allows you to perform cleanup tasks, such as clearing intervals, when a component is unmounted.

import { onCleanup } from 'solid-js';

function Timer() {
  let timerId;
  const [time, setTime] = createSignal(0);

  const startTimer = () => {
    timerId = setInterval(() => setTime(time() + 1), 1000);
  };

  onCleanup(() => clearInterval(timerId));

  return (
    <div>
      <p>Time: {time()}</p>
      <button onClick={startTimer}>Start Timer</button>
    </div>
  );
}

Other packages similar to solid-js

react

React is a popular JavaScript library for building user interfaces. It uses a virtual DOM and a component-based architecture. Compared to Solid.js, React has a larger ecosystem and community but may have more overhead due to its virtual DOM.

vue

Vue.js is a progressive JavaScript framework for building user interfaces. It features a reactive data binding system and a component-based architecture. Vue.js is similar to Solid.js in its reactivity model but offers more built-in features and a larger ecosystem.

svelte

Svelte is a compiler that converts declarative components into efficient imperative code that directly manipulates the DOM. Unlike Solid.js, Svelte does not use a virtual DOM and compiles components at build time, resulting in highly optimized and fast applications.

README

     The Deceptively Simple User Interface Library

Solid is yet another declarative Javascript library for creating user interfaces. It does not use a Virtual DOM. Instead it opts to compile it's templates down to real DOM nodes and wrap updates in fine grained computations. This way when your state updates only the code that depends on it runs.

Key Features

• Real DOM with fine-grained updates (No Virtual DOM! No Dirty Checking Digest Loop!).
• Declarative data
  • Simple composable primitives without the hidden rules.
  • Function Components with no need for lifecycle methods or specialized configuration objects.
• Less than 10% slower vs optimized painfully imperative vanilla DOM code. See Solid on JS Framework Benchmark.
• Tiny in size, 7.07 kB minified and gzipped with all dependencies.
• Supports modern features like JSX Fragments, Portals, Suspense, and Asynchronous Rendering.
• Webcomponent friendly
  • Implicit event delegation with Shadow DOM Retargeting
  • Shadow DOM Portals
  • Custom Element friendly Suspense flow

A Simple Component looks like:

const HelloMessage = ({name}) => (
  <div>
    Hello {name}
  </div>
);

createRoot(() =>
  document
    .getElementById("hello-example")
    .appendChild(<HelloMessage name="Taylor" />)
);

Installation

> npm install solid-js babel-plugin-jsx-dom-expressions

Solid State

It all starts with State. State objects are immutable so to update you call their companion setter function. Through the use of proxies they give the control of an immutable interface and the performance of a mutable one. Note only Plain Objects and Arrays are deeply wrapped.

import { createState, onCleanup } from 'solid-js'

const CountingComponent = () => {
  const [state, setState] = createState({counter: 0});

  const interval = setInterval(() =>
    setState({counter: state.counter + 1})
  , 1000);

  onCleanup(() => clearInterval(interval));

  return <div>{(state.counter)}</div>;
}

You can also deep set:

const [state, setState] = createState({
  user: {
    firstName: 'John'
    lastName: 'Smith'
  }
});

setState('user', {firstName: 'Jake', middleName: 'Reese'});

You can also use functions:

const [state, setState] = createState({counter: 0});
setState('counter', c => c + 1);

This takes the form similar to ImmutableJS setIn for leaving all mutation control at the top level state object. Keep in mind that setState when setting an object attempts to merge instead of replace.

But where the magic happens is with computations(effects and memos) which automatically track dependencies.

createEffect(() =>
  setState({
    displayName: `${state.user.firstName} ${state.user.lastName}`
  })
);

console.log(state.displayName); // Jake Smith

Whenever any dependency changes the State value will immediately update. JSX expressions can also be wrapped in effects so for something as trivial as a display name you could just inline the expression in the template and have it update automatically.

Solid State also exposes a reconcile method used with setState that does deep diffing to allow for automatic efficient interopt with immutable store technologies like Redux, Apollo, or RxJS.

const unsubscribe = store.subscribe(({ todos }) => (
  setState(reconcile('todos', todos)));
);
onCleanup(() => unsubscribe());

Solid Rendering

To accomplish rendering we use JSX for templating that gets compiled to native DOM element instructions. To do that we take advantage of the babel-plugin-jsx-dom-expressions which while converting JSX to DOM element instructions wraps expressions to be wrapped in our computations when indicated by in inner parens {( )}.

JSX as a templating language brings a lot of benefits. The just being javascript goes beyond just not needing a DSL, but setting up closure based context instead of creating context objects. This is more transparent and easier to follow and debug.

To get setup add this babel plugin config to your .babelrc, webpack, or rollup config:

"plugins": ["jsx-dom-expressions"]

And include at the top of your files:

import { r } from 'solid-js/dom'

Or, if you prefer you can use HyperScript. It does come at signifigant performance hit, as it doesn't benefit from any of the compile time optimizations that set Solid apart in performance. But it is an option for those who want to avoid Babel or do not wish to use JSX. Even though it is much slower it is still in the performance category of most popular frameworks. There are some minor differences from how you would write typical HyperScript as you need to manually wrap expressions in functions to make them observable. More information available at babel-plugin-jsx-dom-expressions. Include Solid HyperScript by:

import { h } from 'solid-js/dom'

With HyperScript it is possible to map to element functions or even tagged template literals which offer many different development experiences. See examples below.

Components

Templates in Solid are just Pascal(Capital) cased functions. Their first argument is an props object and return real DOM nodes. Other than that nothing is special about them.

const Parent = () => (
  <section>
    <Label greeting='Hello'>
      <div>John</div>
    </Label>
  </section>
);

const Label = ({greeting, children}) => (
  <>
    <div>{greeting}</div>
    {children}
  </>
);

Since the all nodes from JSX are actual DOM nodes the only responsibility of top level Templates/Components is appending to the DOM. Since change management is independent of code modularization, Solid Templates are sufficient as is to act as Components, or Solid fits easily into other Component structures like Web Components.

import { createState, createRoot } from 'solid-js'

class Component extends HTMLElement {
  constructor () {
    const [state, setState] = createState({});
    const [props, __setProps] = createState({});

    Object.assign(this, {state, setState, props, __setProps});
  }

  connectedCallback() {
    !this.shadowRoot && this.attachShadow({mode: 'open'});

    createRoot(dispose => {
      this.dispose = dispose;
      this.shadowRoot.appendChild(this.render());
    }
  }

  diconnectedCallback() { this.dispose && this.dispose(); }

  attributeChangedCallback(attr, oldVal, newVal) {
    this.__setProps({[attr]: newVal});
  }
}

class MyComponent extends Component {
  constuctor () {
    super();
    this.setState({greeting: 'World'});
  }
  render() {
    return <div>Hello {(state.greeting)}</div>
  }
}

Why?

This project started as trying to find a small performant library to work with Web Components, that had easy interopt with existing standards. It is very inspired by fine grain change detection libraries like Knockout.js and RxJS. The idea here is to ease users into the world of Observable programming by keeping it transparent and starting simple. Classically the Virtual DOM as seen in React for all it's advances has some signifigant trade offs:

• The VDOM render while performant is still conceptually a constant re-render
  • It feels much more imperative as variable declarations and iterative methods for constructing the tree are constantly re-evaluating.
• Reintroduced lifecycle function hell that break apart the declarative nature of the data. Ex. relying on blacklisting changes across the tree with shouldComponentUpdate.
• Homogenous promise of Components and the overly simplistic local state in practice:
  • Imposes boundaries on components to solve performance concerns
  • Prices you into a very specific but not necessarily obvious structure
  • Only served to make it more ambiguous when emerging best practices lead to specialized component classification anyway
• Abstracts debugging to the point a <div /> is not longer just a div
• VDOM libraries still are based around having a specialized data objects.

So the driving questions here are:

• If the data is going to be specialized anyway can we use Proxies to move the complexity into it rather than the rendering while keeping the appearance simple?
• Can this free up existing constraints on how you modularize your view code?
• Does this approach ultimately provide more adaptibility while reducing the API surface?
• Is fine grained change detection fundamentally more performant than the Virtual DOM?

Admittedly it takes a strong reason to not go with the general consensus of best, and most supported libraries and frameworks. And React's Hooks API addresses the majority of what I once considered it's most untenable faults. But I believe there is a better way out there than how we do it today.

I cover this in more detail in my Bring Your Own Framework Blog Series(links below).

Documentation

• State
• Signals
• Rendering
• API

Examples

• Counter on CodePen
• Simple Todos on CodePen
• Simple Routing on CodePen
• Async Effect on CodePen
• Suspense on CodePen
• Redux Undoable Todos on CodePen
• Simple Todos HyperScript on CodePen
• Simple Todos Template Literals on CodePen
• TodoMVC Classic TodoMVC example
• WebComponent Todos Showing off Solid with Web Components
• JS Framework Benchmark The one and only
• UIBench Benchmark a benchmark tests a variety of UI scenarios.
• DBMon Benchmark A benchmark testing ability of libraries to render unoptimized data.
• Sierpinski's Triangle Demo Solid implementation of the React Fiber demo.

Related Projects

• babel-plugin-jsx-dom-expressions The renderer behind Solid.js that enables lightning fast fine grained performance.
• Solid Components Extensions to Solid.js that add a Web Component wrapper and a Context API.
• React Solid State React Hooks API to use Solid.js paradigm in your existing React apps.
• S.js The fine grained change detection engine that drives all computations and tracks all dependencies.

Articles

• Part 1: Writing a JS Framework in 2018
• Part 2: Web Components as Containers
• Part 3: Change Management in JavaScript Frameworks
• Part 4: Rendering the DOM
• Part 5: JS Frameworks in 2019
• How I wrote the Fastest JavaScript UI Framework The key to Solid's performance.
• React Hooks: Has React Jumped the Shark? Comparison of React Hooks to Solid.
• What Every JavaScript Framework Could Learn from React The lessons Solid learned from React.

Status

This project is still a work in progress. While Solid's change management is reaching stability (this repo), I am still refining the rendering API from the Babel Plugin.