Reflex

Fine-Grained Reactive UI Library

"Instant Precision: Reactivity Redefined with Compile-Time Intelligence"

🚀 Why Reflex?

Reflex redefines UI development with a focus on reactivity, efficiency, and extensibility. By leveraging a reactive graph and a Rust-based compiler, Reflex eliminates the overhead of traditional Virtual DOM approaches, delivering predictable performance and a streamlined developer experience.

Key attributes include:

• R — Reactive: Instantaneous, signal-driven updates with no unnecessary re-renders.
• E — Efficient: Optimized through compile-time graph analysis and direct DOM mutations.
• F — Fine-Grained: Precise updates target only changed elements, minimizing computational cost.
• L — Lightweight: ~5–7 KB minified bundle, ideal for mobile and low-bandwidth environments.
• E — Extensible: Plugin-driven reactive graph supports custom nodes and edges.
• X — eXecutable: Direct control over effects and updates, bypassing intermediaries.

Unlike Virtual DOM libraries like React, which rely on diffing and component re-renders, Reflex models the UI as a dynamic reactive graph. A Rust-based compiler analyzes dependencies at build time, reducing runtime overhead and enabling near-native performance. This approach ensures scalability for complex applications while maintaining simplicity for developers.

Reflex prioritizes:

• Signals Over Re-Renders: Updates are confined to actual changes using signal and computed.
• Direct DOM Access: Eliminates diffing, interacting only with affected nodes.
• Adaptive Graph Topology: Components form a reactive graph, optimized at compile time.
• Familiar JSX API: Seamless integration with JSX, compiled to efficient JavaScript.

✨ Core Principles

1. Fine-Grained Reactivity
   signal and computed primitives enable precise, dependency-tracked updates.

2. Direct DOM Operations
   Bypasses Virtual DOM, performing in-place mutations for maximum efficiency.

3. Reactive Effects
   Replaces lifecycle hooks with automated effects, triggered by dependency changes.

4. Streaming SSR + Islands Architecture
   Hydrates only critical components, supporting resumable server-side rendering.

5. Graph-Level Extensibility
   Plugins extend the reactive graph, enabling custom nodes, edges, and behaviors.

6. Compile-Time Optimization
   A Rust-based compiler analyzes the reactive graph, minimizing runtime computations using graph algebra.

🔍 Comparison

Capability	Virtual DOM (e.g., React)	Reflex
State	Hooks/reducers	signal, computed
Updates	Component re-renders	Direct node updates
DOM Rendering	Virtual DOM diffing	Direct DOM calls
Reactivity	Render-driven	Fine-grained signals
SSR	Traditional APIs	Streaming + Resumption + Islands
Lifecycle	Lifecycle hooks	Reactive effects
Extensibility	Hooks/HOCs	Graph-level plugins
Bundle Size	~40–45 KB (minified)	~5–7 KB (minified)
Optimization	Runtime diffing	Compile-time graph analysis

🧠 Why the Name “Reflex”?

"Reflex" reflects the library’s core philosophy: immediate, instinctual responses to state changes. Local updates propagate precisely through the reactive graph, optimized at compile time for responsiveness and simplicity. The name is independent of any external affiliations.

🛠️ The Rust Compiler Advantage

Reflex leverages a Rust-based compiler to analyze the reactive graph at build time, using graph algebra to optimize dependencies and minimize runtime computations. Key benefits include:

• Static Dependency Analysis: Eliminates runtime dependency tracking, reducing overhead.
• Graph Optimization: Applies topological sorting, dead code elimination, and edge merging.
• Cycle Detection: Identifies and resolves cyclic dependencies at compile time.
• WebAssembly Integration: Critical operations compiled to WebAssembly for near-native performance.

This approach makes Reflex up to 2–3x faster than Virtual DOM libraries in dynamic UI scenarios, with a significantly smaller bundle size.

🎯 Reflex: A Reactive Core for the Next Generation

Forget re-renders and complexity. Reflex synchronizes data instantly with any environment, from browsers to mobile apps, using a minimal, high-performance core. It’s not just another framework—it’s a reactive foundation for modern UI development.

📦 Getting Started

Installation:

npm install @reflex/core

Quick Example (JavaScript):

import { signal, computed, effect } from "@reflex/core";

const count = signal(0);
const double = computed(() => count.value * 2);

effect(() => {
  const el = document.getElementById("app");
  if (el) el.textContent = `Count: ${count.value}, Double: ${double.value}`;
});

count.value++; // Updates DOM instantly

JSX Example:

import { signal, computed, render } from "@reflex/core";

function Counter() {
  const count = signal(0);
  const double = computed(() => count.value * 2);

  return (
    <div>
      <p>Count: {count.value}</p>
      <p>Double: {double.value}</p>
      <button onClick={() => count.value++}>Increment</button>
    </div>
  );
}

render(<Counter />, document.getElementById("app"));

The Rust compiler transforms JSX into optimized JavaScript, wiring signals and effects into the reactive graph for direct DOM updates.

📚 Resources

• Documentation: reflex.dev/docs (coming soon)
• GitHub: github.com/reflex-ui/core
• Community: Join discussions on X or Discord

🏁 License

MIT License © 2025 Andrii Volynets

⚖️ Notes

• All product names, logos, and brands are property of their respective owners.
• “React” and related marks are trademarks of Meta Platforms, Inc. Reflex is not affiliated with or endorsed by Meta or any other vendor.
• Package name and branding are subject to change.