LessJS

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The DSD-first Web Components framework. Build static sites with real Shadow DOM, zero JS overhead, and progressive islands.

Quick Start

deno run -A jsr:@lessjs/create my-app
cd my-app && deno task dev

Why LessJS

LessJS renders Web Components on the server via Declarative Shadow DOM. The browser parses DSD natively — no hydration, no JS for static content. Interactive pieces are islands: small, strategy-gated components that load on demand.

// routes/index/index.tsx
import { DsdElement } from '@lessjs/runtime';

export default class HomePage extends DsdElement {
  render() {
    return <h1>Hello LessJS</h1>;
  }
}

The App Shell (<less-layout>) is applied automatically by the Builder — pages only declare their content.

Features

• DSD-first — Server-rendered Shadow DOM. Zero JS overhead for static content.
• JSX + Signals — React-like DX with fine-grained reactivity via alien-signals.
• File-based routing — app/routes/ maps 1:1 to URL paths.
• SSG built-in — Build-time rendering, sitemaps, PWA manifest. Deno-native.
• Progressive islands — client:load | idle | visible | only hydration strategies.
• Hono API routes — Drop API handlers into the route tree.
• Zero-bundler dev — deno task dev:fast cold starts in ~100ms.
• Framework-agnostic — Lit, React, and Vanilla adapters for islands.

Documentation

Section	Link
Guide	lessjs.com/guide/getting-started
API Reference	lessjs.com/apilist
Architecture	lessjs.com/architecture/architecture

Packages

Package	Version	Description
@lessjs/core	v0.28.0	DSD renderer, DsdElement, JSX runtime, islands, navigation
@lessjs/adapter-vite	v0.28.0	Vite plugin: route scanning, SSG pipeline, island entries
@lessjs/ui	v0.28.0	DSD-native UI components (button, card, input, dialog...)
@lessjs/signals	v0.28.0	Signal primitives (signal, computed, effect)
@lessjs/content	v0.28.0	Blog, nav, sitemap build plugins
@lessjs/i18n	v0.28.0	Locales, route expansion
@lessjs/create	v0.28.0	Project scaffold CLI
@lessjs/runtime	v0.28.0	Unified component authoring facade (core + signals + style)

All 19 packages →

What's New in v0.28.0

• Architecture contracts stabilized — createAdapterRegistry() factory, LessRenderer interface expansion, onRenderError hook, try/catch around _renderOrHydrate.
• Full Open Props migration — 7 color scales (indigo/green/red/orange/blue/teal/cyan) with dark mode inversions; 0 custom semantic tokens, 0 hardcoded colors in www/.
• CI composite action — reusable workflow exported, 5-step matrix reduced from 14 to 9 jobs.
• Documentation site theme gates — 80+ test cases covering SSR/CSR theme parity, search/sidebar/TOC color isolation.
• Signal-driven registry — registry index rewritten to zero manual DOM via data-signal + data-signal-attr.
• Full changelog →

Contributing

See CONTRIBUTING.md. Architecture decisions in docs/adr/. Target: v1.0 stable engine freeze.

License

MIT