How can pass the app instance to route file in ExpressJs?

Question

I'm using Express framework to develop my backend APIs, but I encounter with one issue today. I have one server.js (entry) file from there I want to pass app instance to routes/api.js file. where I wanted to check if endpoint prefix is /api/v2 then I want to call the routes/index.js file. But I'm unable to achieve this approach. I'm adding my code of server.js routes/api.js & routes/index.js files below.

Server.js

/** Core Packages */

/** NPM Packages */
const express = require('express');

/** Custom Packages */
const routerApi = require('./routes/api');
const dbConnect = require('./config/database');

const app = express();
dbConnect();

app.use(express.json());
app.use(express.urlencoded({extended: true}));

routerApi(app);

const PORT = 4000;

/** Creating a Server */
const server = app.listen(PORT, () => {
  console.log(`Server running at http://localhost:${PORT}/`);
});

routes/api.js

/** Core Packages */

/** NPM Packages */

/** Custom Packages */

const apiRouter = (app) => {
  app.use('/api/v2', require('./index')(app));
};

module.exports = apiRouter;

routes/index.js

/** Core Packages */

/** NPM Packages */

/** Custom Packages */

const routes = (app) => {
  app.all('/*', (req, res, next) => {
    if (req.path === '/')
      return res.status(200).send({msg: 'Welcome to landing page.'});
  }
}

module.exports = routes;

Error

TypeError: Router.use() requires a middleware function but got a undefined
    at Function.use (/home/admini/Documents/skreem-api-node/node_modules/express/lib/router/index.js:458:13)
    at Function.<anonymous> (/home/admini/Documents/skreem-api-node/node_modules/express/lib/application.js:220:21)
    at Array.forEach (<anonymous>)
    at Function.use (/home/admini/Documents/skreem-api-node/node_modules/express/lib/application.js:217:7)
    at apiRouter (/home/admini/Documents/skreem-api-node/routes/api.js:9:7)
    at Object.<anonymous> (/home/admini/Documents/skreem-api-node/server.js:52:1)
    at Module._compile (internal/modules/cjs/loader.js:816:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:827:10)
    at Module.load (internal/modules/cjs/loader.js:685:32)
    at Function.Module._load (internal/modules/cjs/loader.js:620:12)
    at Function.Module.runMain (internal/modules/cjs/loader.js:877:12)
    at internal/main/run_main_module.js:21:11

Can anyone please help me out to resolve this problem? Any kind of help will be appriciated. Thanks You!

Answer 1

In server.js file, add the following at the bottom of your file:

module.exports = app;

And then require server.js in the files where it is needed:

const app = require('path to server.js file');