Val Town Utilities

A comprehensive collection of utilities for building and testing applications in Val Town Projects.

• readFile - Read files from Val Town vals
• listFiles - List all files in a val
• fetchTranspiledJavaScript - Fetch and transpile TypeScript/JavaScript
• parseVal - Extract metadata from Val Town URLs
• serveFile - Serve files with proper content types
• getContentType - Determine MIME types for files
• staticHTTPServer - Create a static file server
• testServer - Create a test runner with HTML/SVG output

Utilities for reading and managing files in Val Town Projects.

Reads the contents of a file from the current val.

Signature:

Create val
readFile(path: string, metaImportUrl: string): Promise<string>

Example:

Create val
import { readFile } from "https://esm.town/v/std/utils/index.ts";

const content = await readFile("/README.md", import.meta.url);
console.log(content);

Lists all files in the current val with their metadata.

Signature:

Create val
listFiles(metaImportUrl: string): Promise<File[]>

Example:

Create val
import { listFiles } from "https://esm.town/v/std/utils/index.ts";

const files = await listFiles(import.meta.url);
files.forEach((file) => console.log(file.path));

Fetches and transpiles TypeScript/JavaScript code from esm.town URLs.

Signature:

Create val
fetchTranspiledJavaScript(url: string): Promise<string>

Example:

Create val
import { fetchTranspiledJavaScript } from "https://esm.town/v/std/utils/index.ts";

const code = await fetchTranspiledJavaScript(
  "https://esm.town/v/std/utils@85-main/index.ts",
);
console.log(code);

Notes:

• Paths can be specified with or without leading slashes
• TypeScript files are automatically transpiled to JavaScript

Extract metadata about the currently running Val.

Parses Val Town metadata from an import.meta.url.

Signature:

Create val
parseVal(importMetaUrl: string): ValMetadata

Example:

Create val
import { parseVal } from "https://esm.town/v/std/utils/index.ts";

const val = parseVal(import.meta.url);
console.log(val);
// Output: { owner: "username", name: "valname", ... }

Prior Art:

• @pomdtr/extractValInfo
• @easrng/whoami

HTTP utilities for serving val files with proper content types.

Serves a file from the val as an HTTP Response with the correct Content-Type header.

Signature:

Create val
serveFile(path: string, metaImportUrl: string): Promise<Response>

Example:

Create val
import { serveFile } from "https://esm.town/v/std/utils/index.ts";

// In a Hono app
app.get("/assets/*", async (c) => {
  return await serveFile(c.req.path, import.meta.url);
});

Determines the appropriate MIME type for a file based on its extension.

Signature:

Create val
getContentType(path: string): string

Example:

Create val
import { getContentType } from "https://esm.town/v/std/utils/index.ts";

console.log(getContentType("index.html")); // "text/html; charset=utf-8"
console.log(getContentType("script.ts")); // "text/javascript"
console.log(getContentType("data.json")); // "application/json; charset=utf-8"

Features:

• TypeScript/TSX/JSX files are served as text/javascript