@arachnejs/router

Signal-driven router for Arachne: nested layouts, code-split (lazy) routes, per-route data, head/title management, <Link> and link interception, base paths, scroll handling. Runs in the browser, on the server (SSR) and at build time (static prerendering) with the same route table. The path compiler is shared with @arachnejs/server (@arachnejs/router/path). See ADR 0009.

import { browserHistory, createRouter, Link } from "@arachnejs/router";

const routes = [
  {
    path: "/",
    component: (p) => <div class="site"><Nav />{p.children}</div>, // layout
    head: { title: "Home" },
    children: [
      { path: "", component: Home },                                  // index page
      { path: "blog", lazy: () => import("./Blog.tsx") },             // code-split
      {
        path: "blog/:slug",
        component: (p) => <Post post={p.data as Post} />,
        head: ({ data }) => ({ title: (data as Post).title }),
      },
    ],
  },
];

const router = createRouter({
  routes,
  history: browserHistory(),
  base: "/docs",                    // app mounted at site.com/docs
  titleTemplate: "%s · My site",
  load: (match) => fetch(`/data${match.pathname}.json`).then((r) => r.json()), // per-route data
  initialData: window.__DATA__,     // from server-rendered HTML
  fallback: NotFound,
  error: ErrorPage,
});
router.interceptLinks();            // plain <a href="/…"> inside the page route client-side

render(() => <>{router.Outlet()}</>, document.getElementById("app")!);

• Layouts: a route with children renders its component around the matched child (props.children); path: "" is the index child. A layout stays mounted while you navigate between its children (its DOM, scroll positions and local state survive); its params/location/data props update in place. Pages are re-created on every navigation.
• Lazy routes: lazy: () => import("./Page.tsx") (default export or the component) loads before the route commits; router.preload(path) warms it.
• Data: load(match) runs for every navigation; the URL and view switch together when it resolves, router.pending() is true meanwhile, and stale navigations are dropped. Errors render error with props.error.
• Head: static or ({ params, data, location }) => ({ title, meta, links }), merged outer → inner, applied to document on navigation; renderHead(router.head()) produces the server HTML.
• Links: <Link href="/blog"> renders a real <a> (base path applied, aria-current="page" + activeClass when active, prefetch on hover/focus). shouldIntercept skips modified clicks, target, download, rel="external", other origins and unknown paths.
• Scroll: top on push, hash target when present, restored on back/forward (scroll: false to opt out).
• router.Outlet() in a JSX expression is reactive; <router.View /> is the component form.