Express.js Tutorial

Welcome to Express.js Tutorial.

In this series of Express.js Tutorial, we will learn how to get started with Express.js and different concepts of Express.js with well detailed examples.

Get Started with Express.js

Following two tutorials provide you an detailed introduction to Express.js web framework and installation.

What is Express.js? – A brief introduction to Express.js.
Install Express.js – Steps to install express.js using npm.

Express.js Example

Following is a simple example for Express.js application.

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var express = require('express')

// create express application instance
var app = express()
 
// express route
app.get('/', function (req, res) {
   res.send('This is a basic Example for Express.js by TUTORIALKART')
})
 
// start server
var server = app.listen(8000)

In the above code, we created an instance of express application, then defined a router to handle GET requests on URL paht /. Then we started the server to listen on port 8000.

A more detailed example to build a web application and make it run is provided at: Express.js Tutorial – Express.js Example Application.

Express.js Routes

The express.js routes are those that handle a specific HTTP Request on a specified URL path. Following is an example Express route.

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// express route
app.get('/hello/', function (req, res) {
   res.send('This is a basic Example for Express.js by TUTORIALKART')
})

app is the express application instance. We can call HTTP methods like GET (like in the above code snippet), POST, HEAD, COPY, PATCH, MOVE, etc. The first argument is the URL path. The function (second argument to route) gets hooked to paths that match with the path specified. From the above example, the function (req, res) gets hooked to only those requests that have the path baseurl/hello/.

Detailed Express.js Tutorial on Routes – Express.js Routes.

Express.js Middleware

Middlewares are functions that can be executed in an order for a request before sending a response to the client. Following is an example.

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var express = require('express')
var app = express()
 
// define middleware function
function logger(req, res, next) {
   console.log(new Date(), req.url)
   next()
}
 
// calls logger:middleware for each request-response cycle
app.use(logger)

logger is a middleware function, where it can get request and response as arguments. Also next() function to continue with the other functions in the request-response cycle.

Complete Express.js Tutorial on Middleware – Express Middleware.

Express.js Router

Express Router is used to Create independent Router objects.

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Express.js Tutorial