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The Deno Runtime compiles a TypeScript or JavaScript function into a serverless function powered by Deno, running on Vercel.

Usage

Your serverless function file is expected to export default the HTTP handler function, and then vercel-deno takes care of invoking that handler function every time an HTTP request is received.

Note: Check out the api directory to see examples of using popular Deno web frameworks with vercel-deno. Feel free to send a pull request to add additional examples!

Example

Create a file called api/hello.ts with the following contents:

export default () => new Response(`Hello, from Deno v${Deno.version.deno}!`);

Next, define the vercel-deno runtime within the "functions" object in your vercel.json file:

{
	"functions": {
		"api/**/*.[jt]s": { "runtime": "vercel-deno@1.1.0" }
	}
}

Demo: https://vercel-deno.vercel.app/api/hello

Configuration

To configure which flags are passed to deno run, a shebang needs to be defined in the entrypoint of the Serverless Function containing the flags that will be used.

For example, to set the window.location object, and use a specific tsconfig file:

#!/usr/bin/env deno run --location http://example.com/path --config other-tsconfig.json

export default async () => new Response(`Location is ${window.location.href}!`);

There are also a few flags that can be used that are specific to vercel-deno:

  • --version - Specify a specific version of Deno to use (can be any valid Deno release tag β€”Β e.g. v1.2.3).
  • --include-files - Glob pattern of static files to include within the Serverless Function. Can be specified more than once.

Endpoint-specific Environment Variables

It's also possible to specify environment variables that will apply only to a specific API endpoint by utilizing the shebang. Just place the environment variables before the deno command in the shebang. For example:

#!/usr/bin/env FOO=bar ANOTHER="spaces work too" deno run

In this example, the FOO environment variable will be set to "bar" and ANOTHER will be set to "spaces work too" for only this endpoint.

Dynamic Imports

By default, dynamic imports (using the import() function during runtime) will fail. For most use-cases, this is fine since this feature is only necessary for rare use-cases.

However, when dynamic imports are required for your endpoint, the DENO_DIR enviorment variable will need to be set to "/tmp". This is required because the file system is read-only, within the Serverless Function runtime environment, except for the "/tmp" dir. Because dynamic imports will require compilation at runtime, the deno cache directory needs to be writable.

The recommended way of enabling this is to add an environment variable to the endpoint's shebang. For example:

#!/usr/bin/env DENO_DIR=/tmp deno run

export default async () => {
	const mod = await import('http://example.com/mod.ts');
	return new Response(mod.default.doThing());
};

Development

The vercel dev command is supported on Windows, macOS, and Linux:

  • Vercel CLI v19.1.0 or newer is required.
  • Uses the deno binary installed on the system (does not download deno).
  • Specifying a specific version of Deno via --version flag is ignored.