Usage with Express.js

Example app

Description	URL	Links
Express server & procedure calls with node.js.	n/a	CodeSandbox Source

How to add tRPC to existing Express.js project

1. Install deps

bash
yarn add @trpc/server zod

bash
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:

server.ts
ts
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;

server.ts
ts
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.

server.ts
ts
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,
  })
);
app.listen(4000);

server.ts
ts
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,
  })
);
app.listen(4000);

Your endpoints are now available via HTTP!

Endpoint	HTTP URI
getUser	GET http://localhost:4000/trpc/getUser?input=INPUT where INPUT is a URI-encoded JSON string.
createUser	POST http://localhost:4000/trpc/createUser with req.body of type {name: string}