Express is a small framework that sits on top of Node.js’s web server functionality to simplify its APIs and add helpful new features
Perquisites: Follow these steps for project setup and module installation.
Step 1: Create a directory using the below-given command. After creating a directory add the location of the created directory in a terminal.
mkdir <folder_name>
Step 2: Now initialize the npm (node package manager) using the below-given command.
npm init
Step 3: Now Install Express in the present directory and save it in the dependencies list.
npm install express --save
Code Implementation:
app.use(): The app.use() function is used to mount the specified middleware function (are the functions that have access to the request object and response object, or we can call it a response-request cycle) at the path which is being specified. The middleware function is executed when the base of the requested path matches the path.
Syntax:
app.use([path,],callback[,callback...])
// Requiring module const express = require( 'express' )
const app = express() app.use( function (req, res, next) {
console.log( 'hello world' )
next()
}) app.use( function (req, res, next) {
console.log( 'happy holidays' )
next()
}) // Server setup const server = app.listen(8080, function () {
let port = server.address().port
console.log( "Listening at" , port)
}) |
Run the index.js file using the following command:
node index.js
Output:
Index.js
// Requiring module const express = require( 'express' );
const app = express(); app.get( '/' , function (req, res) {
res.send( 'Hello Geek' );
}) // Server setup const server = app.listen(8080, function () {
const host = server.address().address
const port = server.address().port
console.log( " Listening : " , port)
}) |
Run the index.js file using the following command:
node index.js
Output:
Difference between app.use() and app.get() methods:
app.use() method |
app.get() method |
It can be used for making routes modular (like exposing a set of routes from an npm module that other web applications could use). | The method is used to expose the GET method. |
It is intended for binding middleware to your application. The path is a mount path and limits the middleware to only apply any paths requested that begin with it. | It is intended for matching and handling a specific route when requested by get http. |
The middleware function is executed when the base of the requested path matches path. | Routes HTTP GET requests to the specified path with the specified callback functions. |
It will allow for all http requests matching that route. | It will only be allowed for http GET requests to that particular route |
Syntax: app.use([path,],callback[,callback…]) | Syntax: app.get(path, callback) |
Reference:
- https://www.geeksforgeeks.org/express-js-app-use-function/amp/
- https://www.geeksforgeeks.org/express-js-app-get-function/amp/