babel-plugin-reactivars-solid is a Babel plugin that lets you use a Svelte like syntax with Solid (a React version is a WIP).

import { $ } from 'babel-plugin-reactivars-solid'

const getDouble = ({ $sig }) => 
    ({ $doubled: $([
        () => $sig * 2,
        newVal => $sig = newVal / 2

const CounterChild = ({ $doubleCount }) =>
   <button onClick={() => $doubleCount++}>
      {$doubleCount} (click to add 0.5 to count)

const CounterParent = () => {
   let $count = 0
   let { $doubled: $doubleCount } = getDouble({ $sig: $count })
   const incrementCount = () => $doubleCount += 2
   return <>
      <button onClick={incrementCount}>
      <CounterChild {...{ $doubleCount }} />

I'm probably going to make some relatively significant changes to this plugin soon.
I think that I can probably remove some of the complexity and noise with the object literals and destructuring based syntax. Maybe I can even completely remove this whole syntax altogether which will drastically simplify this plugin.
I also think that I can make the read only and write only APIs a lot more consistet with the main syntax.
This can potentially produce significant imporvements to this plugin. Stay tuned!

Disclaimer: this plugin doesn't have any known bugs at the moment, but is still not ready for production use. If you find any bugs please open an issue.

Getting Started

See reactivars-example

npm i -D babel-plugin-reactivars-solid @rollup/plugin-babel

Example config:

import { defineConfig } from 'vite';
import solidPlugin from 'vite-plugin-solid';
import { babel } from '@rollup/plugin-babel';

export default defineConfig({
   plugins: [
            plugins: [
               ["@babel/plugin-syntax-typescript", { isTSX: true }],
            extensions: [".tsx"]
         enforce: 'pre'
   build: {
      target: 'esnext',
      polyfillDynamicImport: false,

Roadmap / Missing Features

  • Examine the possibility of unlocking a better syntax with a TS extension. What I have in mind currently: I want to see if it's possible to use the reactive variable syntax for read-only and write-only reactive variables while maintaining full TS support and eforcing read/write permissions at the language server / linter level. This would be useful for signal accessors and setters as well as memos, wrapped reactive expressions (things like const y = () => x + 1; console.log(y() + 1) could become const $y = x + 1; console.log($y + 1)) and wrapped setters (const setY = y => setX(y + 1); setY(1) could become let $y = y => $x = y + 1; $y = 1). This will help this plugin become more of a consistent language where every reactive value is either a $ prefixed reactive variable/property (reactive property = x.$y) or a property on a JS object / proxy (this should usually appear in props and stores) as well as consistent write syntax for non-store signals. Messing with TS extensions could potentially unlock even better possibilities and it's something I need to explore and think about more, but I really want that additional consistancy which I don't think we can achieve without extending TS, so this alone might be a reason to cross this boundary.
  • Handle batching, update functions and pending values
  • $ label for effects

    Under consideration

  • Reactive variable factory functions (`let $doubleCount = double$($count))
  • Two way binding support for HTML elements

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