Express

Use MeshQL with Express via meshExpressRouter.

Prerequisites

• Node.js 22+
• Express 4 or 5

Install

npm:

npm install meshql-core meshql-http express

JSR:

npx jsr add @meshql/core @meshql/http express

Bun: bun add meshql-core meshql-http express or bunx jsr add @meshql/core @meshql/http && bun add express

Project setup

{
  "type": "module",
  "scripts": {
    "start": "node src/server.js"
  }
}

Server

import { createMesh, buildSelectSql, type MeshSchema } from "@meshql/core";
import { meshExpressRouter } from "@meshql/http/express";
import express from "express";

const schema: MeshSchema = {
  entities: {
    user: { fields: ["id", "name"], table: "users" },
    token: {
      fields: ["accessToken"],
      table: "tokens",
      columns: { accessToken: "access_token" },
    },
  },
  joins: {
    "user.tokens": {
      entity: "token",
      on: "tokens.user_id = users.id",
      type: "many",
    },
  },
};

const mesh = createMesh(schema);

mesh.resolve("user", async (plan) => {
  const { sql, params } = buildSelectSql(plan, schema);
  // Replace with pool.query(sql, params) when using Postgres
  return [{ user_id: 1, user_name: "Ada", tokens_accessToken: "tok_abc" }];
});

const app = express();
app.use(express.json());
app.use(meshExpressRouter(mesh, "/mesh"));

app.listen(3001, () => {
  console.log("MeshQL on http://localhost:3001/mesh");
});

Client test

See Run example for curl commands.

import { createClient } from "@meshql/client";

const client = createClient({ url: "http://localhost:3001/mesh" });

const user = await client.query(
  { user: { $select: { id: true, name: true, tokens: { $select: { accessToken: true } } } } },
  { entityId: "1" },
);

Middleware alternative

import { meshExpressMiddleware } from "@meshql/http/express";

app.use(meshExpressMiddleware(mesh, "/mesh"));

Full example

The express-postgres example includes in-memory and Postgres modes.

Reference

Transport headers, routes, and errors: HTTP adapters.