Using the Node.js Runtime with Vercel Functions

You can create Vercel Function in JavaScript or TypeScript by using the Node.js runtime. By default, the runtime builds and serves any function created within the/api directory of a project to Vercel.

Node.js-powered functions are suited to computationally intense or large functions and provide benefits like:

• More RAM and CPU power: For computationally intense workloads, or functions that have bundles up to 250 MB in size, this runtime is ideal
• Complete Node.js compatibility: The Node.js runtime offers access to all Node.js APIs, making it a powerful tool for many applications

In order to use the Node.js runtime, create a file inside theapi directory with a function using thefetch Web Standard export. No additional configuration is needed:

exportdefault {fetch(request:Request) {returnnewResponse('Hello from Vercel!');  },};

Alternatively, you can export each HTTP method as a separate export instead of using thefetch Web Standard export:

exportfunctionGET(request:Request) {returnnewResponse('Hello from Vercel!');}

To learn more about creating Vercel Functions, see theFunctions API Reference. If you need more advanced behavior, such as a custom build step or private npm modules, see theadvanced Node.js usage page.

Vercel Functions using the Node.js runtime supportall Node.js APIs, including standard Web APIs such as theRequest and Response Objects.

To learn more about the supported Node.js versions on Vercel, seeSupported Node.js Versions.

For dependencies listed in apackage.json file at the root of a project, the following behavior is used:

• Ifbun.lock orbun.lockb is present,bun install is executed
• Ifyarn.lock is presentyarn install is executed
• Ifpnpm-lock.yaml is present,pnpm install is executed
  • Seesupported package managers for pnpm detection details
• Ifpackage-lock.json is present,npm install is executed
• Ifvlt-lock.json is present,vlt install is executed
• Otherwise,npm install is executed

If you need to select a specific version of a package manager, seecorepack.

The Node.js runtime supports files ending with.ts inside of the/api directory as TypeScript files to compile and serve when deploying.

An example TypeScript file that exports a Web signature handler is as follows:

exportdefault {asyncfetch(request:Request) {consturl=newURL(request.url);constname=url.searchParams.get('name')||'World';returnResponse.json({ message:`Hello${name}!` });  },};

You can use atsconfig.json file at the root of your project to configure the TypeScript compiler. Most options are supported aside from"Path Mappings" and"Project References".

Each request to a Node.js Vercel Function gives access to Request and Response objects. These objects are thestandard HTTPRequest andResponse objects from Node.js.

Vercel additionally provides helper methods inside of the Request and Response objects passed to Node.js Vercel Functions. These methods are:

The following Node.js Vercel Function example showcases the use ofrequest.query,request.cookies andrequest.body helpers:

import { VercelRequest, VercelResponse }from"@vercel/node";module.exports= (request:VercelRequest, response:VercelResponse)=> {let who='anonymous';if (request.body&&request.body.who) {    who=request.body.who;  }elseif (request.query.who) {    who=request.query.who;  }elseif (request.cookies.who) {    who=request.cookies.who;  }response.status(200).send(`Hello${who}!`);};

We populate therequest.body property with a parsed version of the content sent with the request when possible.

We follow a set of rules on theContent-type header sent by the request to do so:

With therequest.body helper, you can build applications without extra dependencies or having to parse the content of the request manually.

When the request body contains malformed JSON, accessingrequest.body will throw an error. You can catch that error by wrappingrequest.body withtry...catch:

try {request.body;}catch (error) {returnresponse.status(400).json({ error:'My custom 400 error' });}

Request cancellation must be enabled on a per-route basis. SeeFunctions API Reference for more information.

You can listen for theerror event on the request object to detect request cancellation:

import { VercelRequest, VercelResponse }from'@vercel/node';exportdefaultasync (request:VercelRequest, response:VercelResponse)=> {let cancelled=false;request.on('error', (error)=> {if (error.message==='aborted') {console.log('request aborted');    }    cancelled=true;  });response.writeHead(200);for (let i=1; i<5; i++) {if (cancelled) {// the response must be explicitly endedresponse.end();return;    }response.write(`Count:${i}\n`);awaitnewPromise((resolve)=>setTimeout(resolve,1000));  }response.end('All done!');};

Express.js is a popular framework used with Node.js. For information on how to use Express with Vercel, see the guide:Using Express.js with Vercel.

The Node.js runtime can be used as an experimental feature to run middleware. To enable, add the flag to yournext.config.ts file:

importtype { NextConfig }from'next';constnextConfig:NextConfig= {  experimental: {    nodeMiddleware:true,  },};exportdefault nextConfig;

Then in your middleware file, set the runtime tonodejs in theconfig object:

exportconstconfig= {  matcher:'/about/:path*',  runtime:'nodejs',};