TypeScript & Deno

Automatic type inference in Deno

Deno reads the X-TypeScript-Types header and fetches type definitions automatically:

import { greet, Counter } from "https://my-worker.workers.dev/";

const msg = await greet("World");  // msg: string
const counter = await new Counter(0);
await counter.increment();          // number

No configuration needed. Types are served at /?types and referenced by the header.

Precise types with oxc-parser

At build time, generate-export-types uses oxc-parser to statically analyze your TypeScript source. The resulting types preserve parameter names and types:

// Your source
export function greet(name: string): Promise<string> { ... }
export function add(a: number, b: number): number { ... }
export class Counter {
  constructor(initial?: number);
  increment(): number;
}

// Generated types (served at /?types)
export declare function greet(name: string): Promise<string>;
export declare function add(a: number, b: number): Promise<number>;
export declare class Counter {
  constructor(initial?: number);
  increment(): Promise<number>;
  // ...
}

All return types are wrapped in Promise since every call is async over the network. Private class fields are excluded.

Fetching types manually

# Full type definitions
curl "https://my-worker.workers.dev/?types"

# Per-export types
curl "https://my-worker.workers.dev/greet?types"

Per-export types re-export from the root /?types, so the full definitions are only fetched once.