--- title: Let's make the worst React ever! | daily.dev description: A hands-on walkthrough of building a minimal, deliberately crude React clone from scratch to understand how virtual DOM rendering actually works. Covers... canonical: https://daily.dev/posts/let-s-make-the-worst-react-ever--vxgdt4l4t twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Let's make the worst React ever! | daily.dev og:description: A hands-on walkthrough of building a minimal, deliberately crude React clone from scratch to understand how virtual DOM rendering actually works. Covers... og:url: https://daily.dev/posts/let-s-make-the-worst-react-ever--vxgdt4l4t og:image: https://api.daily.dev/og/posts/vxGDT4L4t.png og:image:alt: Let's make the worst React ever! og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Let's make the worst React ever! **[zserge's blog](https://daily.dev/sources/zserge)** · 9 min read · 0 upvotes · 0 comments ## Summary A hands-on walkthrough of building a minimal, deliberately crude React clone from scratch to understand how virtual DOM rendering actually works. Covers hyperscript-style element creation, a recursive render function that diffs virtual and real DOM nodes, a simple approach to stateful components via a forceUpdate callback, and a custom tagged template literal parser that mimics JSX syntax without a transpiler. The resulting library, called O!, ends up under 1KB minified and is published on GitHub with hooks support added later. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How can I parse JSX-like syntax in JavaScript without using a transpiler? Use tagged template literals to build a small state-machine parser that reads HTML-like markup and converts it into hyperscript calls. The parser tracks three states (text, open tag, close tag), handles placeholders for tag names, attribute values, and children, and returns a nested object structure representing the virtual DOM tree, all without Babel or any build step. _Developers exploring build-free JSX alternatives can find more framework-internals deep dives on daily.dev._ ### How does a minimal virtual DOM diffing algorithm work in plain JavaScript? A minimal render function walks a list of virtual nodes and compares each to the corresponding real DOM child by element type; if they differ, it inserts a newly created node, otherwise it updates changed properties and recurses into children, then removes any leftover DOM nodes past the last rendered virtual node. This achieves basic reconciliation in only a few lines of code. _Anyone learning how virtual DOM diffing works can track more from-scratch framework breakdowns on daily.dev._ ### How small can a JSX-like UI library be when built from scratch in JavaScript? A hand-built library named O! implements hyperscript rendering, a JSX-like tagged-template parser, stateful components, and hooks in under 1KB once minified and compressed. It sacrifices robustness and performance for minimalism, serving mainly as a learning exercise in how frameworks like React work internally rather than a production-ready tool. _Developers comparing tiny framework alternatives can follow more lightweight UI library experiments on daily.dev._ ## Similar posts on daily.dev - [How React Works Internally: Virtual DOM, Reconciliation, and Rendering](https://daily.dev/posts/how-react-works-internally-virtual-dom-reconciliation-and-rendering-en38kquvn) · Medium · 2 upvotes · 0 comments - [React Basics: Thinking in React](https://daily.dev/posts/react-basics-thinking-in-react-bxfmesfzy) · Telerik · 4 upvotes · 0 comments - [The React Handbook for Beginners – JSX, Hooks, and Rendering Explained](https://daily.dev/posts/the-react-handbook-for-beginners-jsx-hooks-and-rendering-explained-c128n6sxb) · freeCodeCamp · 28 upvotes · 0 comments - [React tutorial: Get started with the React JavaScript library](https://daily.dev/posts/react-tutorial-get-started-with-the-react-javascript-library-elwrrjcen) · InfoWorld · 1 upvotes · 0 comments --- Tags: [#webdev](https://daily.dev/tags/webdev), [#javascript](https://daily.dev/tags/javascript), [#react](https://daily.dev/tags/react) [View this post on daily.dev](https://daily.dev/posts/let-s-make-the-worst-react-ever--vxgdt4l4t) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Let's make the worst React ever!","url":"https://daily.dev/posts/let-s-make-the-worst-react-ever--vxgdt4l4t","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/let-s-make-the-worst-react-ever--vxgdt4l4t"},"datePublished":"2026-08-23T10:20:20.682Z","dateModified":"2026-08-23T10:21:14.948Z","description":"A hands-on walkthrough of building a minimal, deliberately crude React clone from scratch to understand how virtual DOM rendering actually works. 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