Parameter express can't be passed with require

Question

app.js

const express = require("express");
const app = express();

app.use("/", require("./routers.js")(app));

app.listen(3000);

router.js

module.exports = function (app) {
  console.log(app);
  app.get("/", (req, res) => {
    res.json(5);
  });
};

The error given by the Console is: " TypeError: Router.use() requires a middleware function but got an undefined "

I don't understand why I can't pass the express app(app.js) through routers( in this way I don't redeclare the express and app variable in router.js ).

Answer 1

Don't pass app to routes better to create a new router and pass to the app.

router.js

const express = require("express");
const router = express.Router();
router.get("/", (req, res) => {
  res.json(5);
});
module.exports = router;

app.js

app.use("/", require("./routers.js"));

As you mention in the comment, you don't have to add an inside app.use

module.exports = function (app) {
  app.get("/", (req, res) => {
    res.json(5);
  });
};

// app.js
require("./routers.js")(app);