질문 백업

var router = express.Router();
router.route('/process/login').post(user.login);
router.route('/process/adduser').post(user.adduser);
router.route('/process/listuser').post(user.listuser);
app.use('/', router);

여기서
app.use('/', router);
var router = express.Router();
router.route('/process/login').post(user.login);
router.route('/process/adduser').post(user.adduser);
router.route('/process/listuser').post(user.listuser);

이렇게 쓰면 오류 나는 이유가 뭘까

오류

C:\Users\장원준\Desktop\upProject\node_modules\express\lib\router\index.js:458
      throw new TypeError('Router.use() requires middleware function but got a ' + gettype(fn));
      ^

TypeError: Router.use() requires middleware function but got a undefined
    at Function.use (C:\Users\장원준\Desktop\upProject\node_modules\express\lib\router\index.js:458:13)
    at EventEmitter.<anonymous> (C:\Users\장원준\Desktop\upProject\node_modules\express\lib\application.js:220:21)
    at Array.forEach (native)
    at EventEmitter.use (C:\Users\장원준\Desktop\upProject\node_modules\express\lib\application.js:217:7)
    at Object.<anonymous> (C:\Users\장원준\Desktop\upProject\app3.js:49:5)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.runMain (module.js:604:10)
    at run (bootstrap_node.js:393:7)
    at startup (bootstrap_node.js:150:9)
    at bootstrap_node.js:508:3