TypeScript

Pages Functions supports TypeScript. You can author any files in your functions/ directory with a .ts extension instead of a .js extension to start taking advantage of TypeScript.

The runtime types can be added to your project by installing the following:

$ npm install --save-dev typescript @cloudflare/workers-types

And then configured by creating a functions/tsconfig.json file:

functions/tsconfig.json
{
  "compilerOptions": {
    "target": "esnext",
    "module": "esnext",
    "lib": ["esnext"],
    "types": ["@cloudflare/workers-types"]
  }
}

If you already have a tsconfig.json at the root of your project, you may wish to explicitly exclude the functions directory to avoid conflicts:

tsconfig.json
{
  "include": ["src/**/*"],
  "exclude": ["functions/**/*"],
  "compilerOptions": {

  }
}

Pages Functions themselves can be typed using the PagesFunction type. This type accepts an Env parameter. You can use it like so:

interface Env {
	KV: KVNamespace;
}

export const onRequest: PagesFunction<Env> = async (context) => {
	const value = await context.env.KV.get('example');
 	return new Response(value);
}