Express Adapter - Trpc

Example app

<table> <thead> <tr> <th>Description</th> <th>Links</th> </tr> </thead> <tbody> <tr> <td>Express server & procedure calls with Node.js.</td> <td> <ul> <li><a href="https://githubbox.com/trpc/trpc/tree/main/examples/express-server">CodeSandbox</a></li> <li><a href="https://github.com/trpc/trpc/tree/main/examples/express-server">Source</a></li> </ul> </td> </tr> </tbody> </table>

How to add tRPC to existing Express 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.

:::tip AI Agents If you use an AI coding agent, install tRPC skills for better code generation:

bash

npx @tanstack/intent@latest install

:::

2. Create a tRPC router

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

import { initTRPC } from '@trpc/server';
import { z } from 'zod';

export const t = initTRPC.create();

export const appRouter = t.router({
  getUser: t.procedure.input(z.string()).query((opts) => {
    opts.input; // string
    return { id: opts.input, name: 'Bilbo' };
  }),
  createUser: t.procedure
    .input(z.object({ name: z.string().min(5) }))
    .mutation(async (opts) => {
      // use your ORM of choice
      return { id: '1', ...opts.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 adapter

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

import { initTRPC } from '@trpc/server';
import * as trpcExpress from '@trpc/server/adapters/express';
import express from 'express';

// created for each request
const createContext = ({
  req,
  res,
}: trpcExpress.CreateExpressContextOptions) => ({}); // no context
type Context = Awaited<ReturnType<typeof createContext>>;

const t = initTRPC.context<Context>().create();
const appRouter = t.router({
  // [...]
});

const app = express();

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} |