--- name: val-town-bbf5a6dc2ac8 description: >- Write and deploy server-side TypeScript functions instantly with Val Town. Use when someone asks to "deploy a function quickly", "serverless TypeScript", "quick API endpoint", "webhook handler", "cron job in the cloud", "Val Town", "instant API without infrastructure", or "deploy a script without a server". Covers HTTP, cron and email triggers, SQLite storage, environment variables, and the vt CLI. license: Apache-2.0 compatibility: "Browser, or the vt CLI (needs Deno). Deno-based TypeScript runtime." metadata: author: terminal-skills version: "1.1.0" category: development tags: "serverless, typescript, functions, val-town, cron" --- # Val Town ## Overview Val Town is a platform for writing and deploying TypeScript and JavaScript instantly: no infrastructure, no build step. A val is a versioned folder of files that is deployed as you edit, like a repository that can run. A file can be triggered by an HTTP request, a schedule (cron) or an incoming email, and each val has a private SQLite database, blob storage, environment variables, and npm or URL imports. The runtime is Deno. Changes deploy within about 100 ms. ## When to Use - A quick API endpoint or webhook handler (minutes, not hours) - Scheduled tasks without managing servers - Prototyping before building proper infrastructure - Glue code between services (fetch from API A, transform, POST to API B) - Small amounts of data in the built-in SQLite database ## Instructions Create a val in the browser (name it, then use "+ Add trigger" on a file to choose HTTP, Cron or Email) or from your machine with the `vt` CLI. HTTP vals are served at `[name].val.run`. ### HTTP trigger (API endpoint) The default export takes a standard `Request` and returns a `Response` (frameworks such as Hono work too). ```typescript // index.http.tsx (HTTP trigger) export default async function (req: Request): Promise { const url = new URL(req.url); if (req.method === "GET") { const name = url.searchParams.get("name") ?? "World"; return Response.json({ message: `Hello, ${name}!` }); } if (req.method === "POST") { const body = await req.json(); return Response.json({ received: body, timestamp: Date.now() }); } return new Response("Method not allowed", { status: 405 }); } ``` ### Cron trigger (scheduled task) The handler receives an `Interval` (`{ lastRunAt: Date | undefined }`); its return value is ignored. Schedules are either a simple interval or a cron expression, always evaluated in UTC. The Free plan allows a run every 15 minutes at most, Pro every minute. ```typescript // daily-report (cron trigger) export default async function (interval: Interval) { const response = await fetch("https://api.northwind.dev/v1/stats/daily"); const stats = await response.json(); await fetch(Deno.env.get("SLACK_WEBHOOK_URL")!, { method: "POST", headers: { "Content-Type": "application/json" }, body: JSON.stringify({ text: `Daily report since ${interval.lastRunAt ?? "first run"}: ${stats.signups} signups` }), }); } ``` ### Email trigger Each email val gets an address like `yourname@valtown.email`. The handler receives an `Email` object (`from`, `to`, `subject`, `text`, `html`, `attachments`, `headers`); inbound mail, attachments included, must be under 30 MB. ```typescript // inbox (email trigger) export default async function (email: Email) { console.log("Email received", email.from, email.subject); for (const file of email.attachments) console.log(`Attachment: ${file.name}`); } ``` ### SQLite storage Every val has its own private SQLite database (Turso-backed; 10 MB on Free, up to 1 GB on Pro). The older per-account global database is legacy. Results have `columns`, `rows`, `rowsAffected` and `lastInsertRowid`. ```typescript // todos.http.tsx import { sqlite } from "https://esm.town/v/std/sqlite/main.ts"; await sqlite.execute(` CREATE TABLE IF NOT EXISTS todos ( id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT NOT NULL, done INTEGER DEFAULT 0, created_at DATETIME DEFAULT CURRENT_TIMESTAMP ) `); export default async function (req: Request): Promise { const url = new URL(req.url); if (req.method === "GET") { const result = await sqlite.execute("SELECT * FROM todos ORDER BY created_at DESC"); return Response.json(result.rows); } if (req.method === "POST") { const { title } = await req.json(); await sqlite.execute({ sql: "INSERT INTO todos (title) VALUES (:title)", args: { title } }); return Response.json({ ok: true }, { status: 201 }); } if (req.method === "DELETE") { const id = Number(url.searchParams.get("id")); await sqlite.execute({ sql: "DELETE FROM todos WHERE id = :id", args: { id } }); return Response.json({ ok: true }); } return new Response("Not found", { status: 404 }); } ``` Use `sqlite.batch([...])` to run several statements together. ### Webhook handler with signature check ```typescript // stripe.http.tsx import Stripe from "npm:stripe"; const stripe = new Stripe(Deno.env.get("STRIPE_SECRET_KEY")!); export default async function (req: Request): Promise { const signature = req.headers.get("stripe-signature")!; const body = await req.text(); let event; try { event = await stripe.webhooks.constructEventAsync( body, signature, Deno.env.get("STRIPE_WEBHOOK_SECRET")!, undefined, Stripe.createSubtleCryptoProvider(), ); } catch { return new Response("Invalid signature", { status: 400 }); } if (event.type === "checkout.session.completed") { console.log("Paid:", event.data.object.id); } return Response.json({ received: true }); } ``` ### Working locally with vt ```bash deno install -grAf jsr:@valtown/vt # install (requires Deno) vt # first run: sign in and create an API key vt clone maria/invoice-webhook # also: vt create, vt pull, vt push, vt watch, vt tail ``` Set `VAL_TOWN_API_KEY` instead of the browser sign-in in CI. `vt push` overwrites without asking; `vt pull` may prompt. ## Examples ### Example 1: Quick monitoring endpoint **User prompt:** "I need a quick URL that checks if my website is up and returns the status." Create an HTTP val whose handler does `const start = Date.now(); const res = await fetch("https://shop.northwind.dev/health")` and returns `Response.json({ up: res.ok, status: res.status, ms: Date.now() - start })`. Opening `https://[name].val.run` shows `{"up":true,"status":200,"ms":143}`. ### Example 2: GitHub webhook to Slack **User prompt:** "When someone stars my GitHub repo, send a message to my Slack channel." Create an HTTP val, add `SLACK_WEBHOOK_URL` in the val's environment variables, and point a GitHub webhook (event "Watch") at the val URL. The handler checks `req.headers.get("x-github-event") === "watch"`, then POSTs `{ text: "New star from " }` to Slack. A star shows up in the channel within seconds. ## Guidelines - Handlers are standard Web API: `Request` in, `Response` out. - Read secrets with `Deno.env.get("NAME")` or `process.env.NAME`; set them in the val's settings. Changes apply on the next request without redeploying, and code cannot change them at runtime. Never hard-code keys: public vals expose their source (values stay hidden). - Free plan: unlimited public vals, 100,000 runs a day, 1 minute wall-clock time per run, 15-minute cron minimum, 3 days of logs, no private vals or custom domains. Pro raises these (private vals, 1-minute cron, 10-minute runs). Check val.town/pricing for current numbers. - npm packages use the `npm:` specifier; other vals import by URL from `esm.town`. - Always verify webhook signatures (Stripe, GitHub) before acting on the payload. - Cron expressions are UTC; the Free plan cannot run more often than every 15 minutes. - Best for webhooks, cron and prototypes; use dedicated infrastructure for high-traffic or latency-critical production APIs. --- Source attribution: terminal-skills Original project: https://github.com/TerminalSkills/skills/blob/8a9852d489f274538be9bf1c9121aeb403750b1c/skills/val-town/SKILL.md License: Apache-2.0 License information: https://www.apache.org/licenses/LICENSE-2.0 Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. Definitions. 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See the License for the specific language governing permissions and limitations under the License. # Mega AI Hub resource metadata Creator / publisher: terminal-skills Original project: https://github.com/TerminalSkills/skills/blob/8a9852d489f274538be9bf1c9121aeb403750b1c/skills/val-town/SKILL.md Attribution basis: Source repository record Fields of work: Development & Engineering, Product Management Roles: Backend Developer, Product Manager, Growth Product Manager, DevOps / SRE, Data Engineer Specialties: Backend Tools: Val Town Country applicability: Country not specified Classification basis: Source category, role and specialization labels Instruction SHA-256: 79e549e4733396e9066cab9b3fecaddb3581e7be4538bcbf4669e01cfc7ebd38