throw new TypeError('Router.use() requires a middleware function but got a + gettype(fn)). (other problem)

Question

hi, i'm writing a application under NodeJS but got the following error:

throw new TypeError('Router.use() requires a middleware function but got a ' + gettype(fn)) ^

TypeError: Router.use() requires a middleware function but got a Object at Function.use (C:\Users\decopiapo\restserver1221\node_modules\express\lib\router\index.js:458:13) at Function. (C:\Users\decopiapo\restserver1221\node_modules\express\lib\application.js:220:21) at Array.forEach () at Function.use (C:\Users\decopiapo\restserver1221\node_modules\express\lib\application.js:217:7) at Server.routes (C:\Users\decopiapo\restserver1221\models\server.js:58:14) at new Server (C:\Users\decopiapo\restserver1221\models\server.js:19:14) at Object. (C:\Users\decopiapo\restserver1221\app.js:3:16) at Module._compile (node:internal/modules/cjs/loader:1101:14) at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10) at Module.load (node:internal/modules/cjs/loader:981:32) [nodemon] app crashed - waiting for file changes before starting...

The Code is:

const {Router} = require('express');

const { check } = require('express-validator');

const { login} = require('../controllers/auth');

const { validatefields } = require('../middlewares/validate-fields');

const router = Router();

router.post('/login', [

check('email', 'Email is mandatory').isEmail(),

check('password', 'The Password is mandatory').not().isEmpty(),

validatefields

],

login);

module.exports = { router }

....

note

If i change "module.exports = { router }" for "module.exports = router" the problem disappears, but what if i want to export a constant or other function?

example:

const {Router} = require('express');

const { check } = require('express-validator');

const { login} = require('../controllers/auth');

const { validatefields } = require('../middlewares/validate-fields');

const myvar = '12321@as';

const router = Router();

router.post('/login', [

check('email', 'Email is mandatory').isEmail(),

check('password', 'The Password is mandatory').not().isEmpty(),

validatefields

],

login);

module.exports = { router, myvar }

the error appears again...

throw new TypeError('Router.use() requires a middleware function but got a ' + gettype(fn)) ^

TypeError: Router.use() requires a middleware function but got a Object at Function.use

How i can solve this problem. Any Ideas?

Node Version: v16.11.1 - Express Version : 4.17.1

try `module.exports = router ` https://stackoverflow.com/questions/27465850/typeerror-router-use-requires-middleware-function-but-got-a-object — cmgchess, Jan 12 '22 at 19:01
the problem is when I need to export more than one function or constant, it generates that error. to export more than one I need to do "module.exports = { router, myfunction }" and that's doesn't work. — Frank alexander Rivera Fernand, Jan 12 '22 at 19:34

traynor · Answer 1 · 2022-01-12T22:09:11.997

You can export it as you like, the problem is how you're requiring and using it.

Check your server file, if you export it like this:

// some router
module.exports = {myRouter, myvar};

then you need to use it like this:

// app
app.use('/some-routes', someRoutes.myRouter);

or you can handle it at the require step:

//app
const someRoutes = require('./routes/some-routes').myRouter;
//...
app.use('/some-routes', someRoutes);

throw new TypeError('Router.use() requires a middleware function but got a + gettype(fn)). (other problem)

1 Answers1