Currently, I am working with TypeScript and Express to develop an API that adheres to the principles of Clean Architecture. To organize my application, I have structured each route in separate folders and then imported them all into an index.ts file where I merge them into a single router before exporting. However, I am facing an issue where the imported file is returning undefined.
Despite TypeScript correctly inferring the type of the imported file without any errors during development, the problem only arises when attempting to run the code:
TypeError:
app.use()requires a middleware function
The snippet of code causing the error is as follows:
// expressInstance.ts --> Imported by the "server.ts" file, where listening the server happens
import express from "express";
import cors from "cors";
import { router } from ".."; // File with all the routes
const expressInstance = express();
expressInstance.use(express.urlencoded({extended: false}));
expressInstance.use(express.json());
expressInstance.use(cors());
expressInstance.use(router); // Line where the error appears
export {
expressInstance
};
The code from the imported router file is as follows:
// index.ts
import { Router } from "express";
import { userRouter } from "./user.routes";
import { postRouter } from "./post.routes";
const router = Router();
router.use("/user", userRouter);
router.use("/post", postRouter);
export {
router
};
Although I came across a related question mentioning that the issue of returning undefined used to happen in Express version 3, I am using version 4.17.13, ruling out that possibility. I am currently unsure of what might be causing this problem. I attempted to log the content of the router using console.log(router) in the index.ts file before it was imported by expressInstance.ts, but the code didn't execute at all.