A tiny but blazing fast router for Vercel serverless functions.

readme.md

Vercel Router

A tiny but blazing fast router for Vercel serverless functions.

Usage

import { router } from '...';

let app = router({
  basePath: '/api',
  allowCors: true
});

// Support for path params
app.get('/something/:id', (req, res) => {
  res.send('Something: ' + req.params.id);
});

app.post('/route', (req, res) => {
  res.send('POST /route');
});

app.all('/*', (req, res) => {
  res.status(404).send('Not found');
});

// Let Vercel execute the router
export default app.run;

vercelRouter.ts

import { VercelRequest, VercelResponse } from '@vercel/node'

export interface Request extends VercelRequest {
  params: { [key: string]: string }
}

export type Handler = (req: Request, res: VercelResponse) => unknown;

interface Route {
  match: string;
  handler: Handler;
  method: string;
}

let match = (path: string, route: Route) => {
  let match = path.match(route.match);
  if (!match) return false;
  return match.groups || {};
};

export let router = ({ basePath, allowCors }: {
  basePath?: string,
  allowCors?: boolean
}) => {
  if (!basePath) basePath = '';
  if (basePath.endsWith('/')) basePath = basePath.slice(0, -1);

  let routes: Route[]

  let addRoute = (method: string, route: string, handler: Handler) => {
    routes.push({
      match: `^${(basePath + route)
         .replace(/(\/?)\*/g, '($1.*)?')
         .replace(/\/$/, '')
         .replace(/:(\w+)(\?)?(\.)?/g, '$2(?<$1>[^/$3]+)$2$3')
      }\/*$`,
      handler,
      method: method.toUpperCase()
    })
  };

  let run = (baseReq: VercelRequest, res: VercelResponse) => {
    if (allowCors) {
      res.setHeader('Access-Control-Allow-Credentials', 'true')
      res.setHeader('Access-Control-Allow-Origin', '*')
      res.setHeader('Access-Control-Allow-Methods', 'GET,OPTIONS,PATCH,DELETE,POST,PUT')
      res.setHeader(
        'Access-Control-Allow-Headers',
        'X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Api-Version'
      )
    
      if (baseReq.method === 'OPTIONS') {
        res.status(200).end('');
        return
      }
    }

    let path = new URL(baseReq.url, `http://${baseReq.headers.host}`).pathname;

    for (let route of routes) {
      if (baseReq.method != route.method && route.method != 'ALL') continue; 
      let params = match(path, route);

      if (params) {
        let req: Request = Object.assign(baseReq, { params });
        route.handler(req, res);
      }
    }
  }

  return {
    run, 
    all: (route: string, handler: Handler) => addRoute('ALL', route, handler),
    get: (route: string, handler: Handler) => addRoute('GET', route, handler),
    post: (route: string, handler: Handler) => addRoute('POST', route, handler),
    put: (route: string, handler: Handler) => addRoute('PUT', route, handler),
    patch: (route: string, handler: Handler) => addRoute('PATCH', route, handler),
    delete: (route: string, handler: Handler) => addRoute('DELETE', route, handler),
    head: (route: string, handler: Handler) => addRoute('HEAD', route, handler),
    options: (route: string, handler: Handler) => addRoute('OPTIONS', route, handler),
  }
}