Handling different routes in express.js

Node.js Server Side Programming Programming

For handling different routes, use() function is used. use() function has multiple overloaded version, one of version also takes url path as a argument. Based on the url path, the requests will be filtered out for respective middleware.

const http = require('http');
const express = require('express');
const app = express();
app.use('/', (req, res,next)=>{
   console.log('first middleware');
   res.send('<h1> first midleware:
   Hello Tutorials Point </h1>');
});
const server = http.createServer(app);
server.listen(3000);

in above example we used ‘/’ as url path, it’s a default.

Now, as every route starts with ‘/’, the above middleware executes for every http request. It works for ‘/’ and for ‘/username’ as well.

To avoid above problem , we will have to use path specific middleware first before default middleware.

const http = require('http');
const express = require('express');
const app = express();
app.use('/username', (req, res,next)=>{
   res.send('<h1> My username </h1>');
});
app.use('/', (req, res,next)=>{
   console.log('first middleware');
   res.send('<h1> first midleware: Hello Tutorials Point </h1>');
});
const server = http.createServer(app);
server.listen(3000);

Now, we used ‘/username’ path middleware first and as we have not used next() in the it , it will not pass the http request to next middleware.

So we see browser output like below for different urls −

localhost:3000

For localhost:3000/username

If any pre-processing on http request requires for all, the using default middleware url path ‘/’ can be useful. Just we will have to use next() in it to pass the request after pre-processing to next middlewares.

const http = require('http');
const express = require('express');
const app = express();
app.use('/', (req, res,next)=>{
   console.log('log request info', req);
   next();
});
app.use('/username', (req, res,next)=>{
   res.send('<h1> My username </h1>');
});
app.use('/', (req, res,next)=>{
   console.log('first middleware');
   res.send('<h1> first midleware: Hello Tutorials Point </h1>');
});
const server = http.createServer(app);
server.listen(3000);

Shyam Hande

Updated on 13-May-2020 13:20:49

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