Example app​

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Express server & procedure calls with node.js.

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How to add tRPC to existing Express.js project​

1. Install deps​

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;

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);

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}