Deno Frontend Agent Skill

Frontend development with Deno

Two paths. Pick by what the project already uses.

Regular npm frameworks — the usual choice

Deno runs the normal frontend ecosystem: React, Vue, Svelte, Solid, Vite, Astro,

Next.js, Nuxt, SvelteKit, Remix, SolidStart. Nothing needs to be ported, and

there is no Deno-specific way to write them.

deno create vite my-app     # or astro, next, nuxt, svelte…
cd my-app
deno install
deno task dev

deno create is npm create. deno install reads package.json.

deno task <script> runs package.json scripts. That is the whole difference.

Follow the framework's own documentation for everything else — routing,

components, data loading, and config are the framework's concern, not Deno's.

Don't invent Deno-flavoured variants of their APIs, and don't reach for Fresh

patterns in a React or Svelte project.

The only things worth knowing:

• Some frameworks need "nodeModulesDir": "auto" in deno.json; Next.js does.
• Permissions apply to the dev server too — framework tasks generally want -A.
• Deploying: see the deno-deploy skill, which lists per-framework build

commands and presets.

Fresh — Deno's own framework

Fresh suits a new Deno-first project that wants server rendering with minimal

client JavaScript. It uses island architecture: pages render on the server,

and only components in islands/ ship JavaScript.

deno run -Ar jsr:@fresh/init
cd my-project
deno task dev                # http://localhost:5173

A Fresh project is Vite-based: vite.config.ts for the build, main.ts for the

server, file-based routes in routes/, islands in islands/, server-only

components in components/. Preact supplies the component model, with signals

for state.

// islands/Counter.tsx — interactive, ships JS
import { useSignal } from "@preact/signals";

export default function Counter() {
  const count = useSignal(0);
  return <button onClick={() => count.value++}>Count: {count.value}</button>;
}

Three rules carry most of the weight:

• Islands ship JavaScript — keep them small, leave everything else in

components/.

• Island props must be serializable. Functions cannot be passed.
• Handlers take a single (ctx) parameter.

Load references/FRESH.md for routes, handlers, define helpers, middleware,

islands, signals, and Tailwind.

Use Fresh 2.x, imported from "fresh". For an existing 1.x project, or one

pinned to a 2.0.0-alpha.* release, see references/FRESH_MIGRATION.md.

Further reading

• <https://fresh.deno.dev/docs> — Fresh documentation
• references/FRESH.md — Fresh 2.x patterns in depth
• references/FRESH_MIGRATION.md — Fresh 1.x and alpha migration