Express app.use routes with optional params

Question

I'm trying to add optional parameters to Express in all of my routes. Here is a part of my code:

const express = require('express');
const bodyParser = require('body-parser');
const apiRoutes = require('./routes/apiRoutes');

const app = express();
const port = process.env.PORT || 3000;

app.use(
    '/api/:param?',
    bodyParser.json({ limit: '50mb' }),
    bodyParser.urlencoded({ extended: false, parameterLimit: 50000 }),
    apiRoutes,
);
const server = app.listen(port, () => {
  console.log(`Server is started on port *:${port}`);
});

I have all of my routes in apiRoutes file defined like:

router.get('system/versionInfo', async (req, res) => {
    console.log('return Version info');
});

router.get('system/info', async (req, res) => {
    console.log('return system info');
});

I would like the param? to be optional so sometimes will be passed sometimes not. Now if I do not pass that param , the routes are returning 404 error (Not Found). If I pass it, all is working fine.

So for example if I run:

'/api/test/system/versionInfo'

all is fine, but if I run

'/api/system/versionInfo'

it returns 404. I would like in both cases to return valid route.

Answer 1

Since express will go over all routes looking for a match, you can pass your apiRoutes to multiple app.use() calls, like this:

in apiRoutes.js:

router.get('system/info', async (req, res) => {
  console.log('return system info');
});

in app.js:

app.use('/api/:param?',
  (req, res, next) => {
    if (req.params.param == "test") console.log("test param detected");
    next();
  },
  apiRoutes,
);

app.use('/api', apiRoutes);

The /api/test/system/info route will match the first rule, the api/system/info route will match the second rule.