Usage with Express.js

Example app

How to add tRPC to existing Express.js project

1. Install deps

yarn add @trpc/server zod

Zod isn’t a required dependency, but it’s used in the sample router below.

2. Create a tRPC router

Implement your tRPC router. A sample router is given below:

import * as trpc from '@trpc/server';
import { z } from 'zod';
const appRouter = trpc
  .router()
  .query('getUser', {
    input: z.string(),
    async resolve(req) {
      req.input; // string
      return { id: req.input, name: 'Bilbo' };
    },
  })
  .mutation('createUser', {
    // validate input with Zod
    input: z.object({ name: z.string().min(5) }),
    async resolve(req) {
      // use your ORM of choice
      return await UserModel.create({
        data: req.input,
      });
    },
  });
// export type definition of API
export type AppRouter = typeof appRouter;

If your router file starts getting too big, split your router into several subrouters each implemented in its own file. Then merge them into a single root appRouter.

3. Use the Express.js adapter

tRPC includes an adapter for Express.js out of the box. This adapter lets you convert your tRPC router into an Express.js middleware.

import * as trpcExpress from '@trpc/server/adapters/express';
const appRouter = /* ... */;
const app = express();
// created for each request
const createContext = ({
  req,
  res,
}: trpcExpress.CreateExpressContextOptions) => ({}) // no context
type Context = trpc.inferAsyncReturnType<typeof createContext>;
app.use(
  '/trpc',
  trpcExpress.createExpressMiddleware({
    router: appRouter,
    createContext: () => null, // no context
  })
);
app.listen(4000);

Your endpoints are now available via HTTP!