react-svelte VS uibuilder

React’s changes over time have always been broadly compatible, and the same under the hood, just presented and manipulated a different way at the surface. Migrating to anything like Svelte would be a radical and extremely incompatible change on multiple fronts. It’s never, ever going to happen; the closest you’ll get will be another layer on top of React that embeds something like Svelte—such as https://github.com/Rich-Harris/react-svelte.

Svelte’s approach requires detailed knowledge of the structure of state, and requires compilation: components’ blocks are not written in JavaScript, but rather a language with the same general syntax but different semantics, and some places where JavaScript is too flexible to be tractable get replaced with special template syntax (like {#each} instead of for-loops or Array.prototype.map). Svelte cannot be implemented as a JavaScript library (I disqualify eval()). Svelte is also deliberately severely limited in what it can express in various places, whereas React gives you the full power of JavaScript (for better and for worse).<p>You could perhaps implement an optimising compiler for a small subset of React components that avoid problematic patterns and are written in TypeScript with proper specifications of the types of state and props; but if you considered it unacceptable for this compiler to change the component’s semantics, I think you’d be surprised at how little serious React code in the wild could actually be supported. Even simple loops <i>might</i> be out of reach. The Svelte approach can’t be a progressive enhancement, it’s an all-or-nothing (at the component level).

This looks bad. I see custom syntax, and JavaScript embedded into HTML in a way that cannot be syntax-checked at build time.

If you want a lightweight framework check out UIBuilder instead: https://github.com/wisercoder/uibuilder

Same JSX syntax as React, but this lib is very simple -- just over 200 lines of source code.

If you don't need Virtual DOM then Web Components are a great idea for building reusable components that work with all frameworks, including React. You can even use JSX to build Web Components: https://github.com/wisercoder/uibuilder