JS export modules - official docs + tut

express.Router

Use the express.Router class to create modular, mountable route handlers. A Router instance is a complete middleware and routing system; for this reason, it is often referred to as a “mini-app”.

The following example creates a router as a module, loads a middleware function in it, defines some routes, and mounts the router module on a path in the main app.

Create a router file named birds.js in the app directory, with the following content:

var express = require('express')
var router = express.Router()

// middleware that is specific to this router
router.use(function timeLog (req, res, next) {
  console.log('Time: ', Date.now())
  next()
})
// define the home page route
router.get('/', function (req, res) {
  res.send('Birds home page')
})
// define the about route
router.get('/about', function (req, res) {
  res.send('About birds')
})

module.exports = router

Then, load the router module in the app:

var birds = require('./birds')

// ...

app.use('/birds', birds)

The app will now be able to handle requests to /birds and /birds/about, as well as call the timeLog middleware function that is specific to the route.

Configurable middleware

If you need your middleware to be configurable, export a function which accepts an options object or other parameters, which, then returns the middleware implementation based on the input parameters.

File: my-middleware.js

module.exports = function (options) {
  return function (req, res, next) {
    // Implement the middleware function based on the options object
    next()
  }
}

The middleware can now be used as shown below.

var mw = require('./my-middleware.js')

app.use(mw({ option1: '1', option2: '2' }))

Refer to cookie-session and compression for examples of configurable middleware.

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server/index.js

const express = require('express');
const createError = require('http-errors');
const path = require('path');
const configs = require('./config');
const SpeakerService = require('./services/SpeakerService');
const app = express();

const config = configs[app.get('env')];

const speakerService = new SpeakerService(config.data.speakers);

app.set('view engine', 'pug');
if(app.get('env') === 'development') {
    app.locals.pretty = true;
}
app.set('views', path.join(__dirname, './views'));
app.locals.title = config.sitename;

const routes = require('./routes');
app.use(express.static('public'));
app.get('/favicon.ico', (req, res, next) => {
    return res.sendStatus(204);
});

app.use(async (req, res, next) => {
    try {
        const names = await speakerService.getNames();
        res.locals.speakerNames = names;
        return next();
    } catch(err) {  
        return next(err);
    }
});

app.use('/', routes({
    speakerService
}));

app.use((req, res, next) => {
    return next(createError(404, 'File not found'));
});

app.use((err, req, res, next) => {
    res.locals.message = err.message;
    const status = err.status || 500;
    res.locals.status = status;
    res.locals.error = req.app.get('env') === 'development' ? err : {};
    res.status(status);
    return res.render('error');
});

app.listen(3000);

module.export = app;

server/routes/index.js

const express = require('express');

const router = express.Router();

const speakersRoute = require('./speakers');
const feedbackRoute = require('./feedback');

module.exports = (param) => {
    
    const { speakerService } = param;

    router.get('/', async (req, res, next) => {
        
        const speakerslist = await speakerService.getListShort();

        return res.render('index', {
            page: 'Home',
            speakerslist,
        });
    });

    router.use('/speakers', speakersRoute(param));
    router.use('/feedback', feedbackRoute(param));
    
    return router;
};

server/routes/speakers/index.js

const express = require('express');

const router = express.Router();

module.exports = (param) => {

    const { speakerService } = param;

    router.get('/', async (req, res, next) => {
        const speakerslist = await speakerService.getList();
        return res.render('speakers', {
            page: 'All Speakers',
            speakerslist
        });
    });

    router.get('/:name', (req, res, next) => {
        return res.render('speakers/detail', {
            page: req.params.name,
        });
    });
    
    return router;
};