What is express middleware

Middleware functions are functions that have access to the request object (req), the response object (res), and the next function in the application’s request-response cycle. The next function is a function in the Express router which, when invoked, executes the middleware succeeding the current middleware.

Major task of middleware

• Execute any code.
• Make changes to the request and the response objects.
• End the request-response cycle.
• Call the next middleware in the stack.

Example

1. First Create new node application and create package.json , index.js and install node modules express and body- praser by following commands.

   npm install express
   npm install body-parser

    

2.  Write following code into index.js

   var express = require('express')
   var app = express()
   const bp= require('body-parser')
   
   app.use(bp.urlencoded({extended: false}));
   app.use(bp.json());
   
    var mfun = function(req, res, next)
    {
      console.log('middleware is called');
      console.log(req.body.name);
      console.log(req.body.fname);
      next();
    }
    app.use(mfun);
   app.get('/', function (req, res) {
     res.send('GET Request')
   })
   app.post('/', function (req, res) {
     res.send('POST Request')
   })
   app.listen(3000)

    

3. Run the program and start postman to see results

   nodemon index.js

    

   Output