Middleware is a simple javascript function with three parameters request, response and next

Apart from handling http request it can perform the following tasks:

• Manipulate request and response objects
• Perform isolated tasks
• Terminate request flow by sending response
• Pass the control to another middleware

We load middleware in express by use() of the express app.

var express = require('express');
var app = express();
app.use(function (req, res, next){
	// Your code
	// to pass the control invoke next() at the end
	next();	
});

Here,
– req is the request object.
– res is the response object.

Click Here to find github example