What is ExpressJS?

Introduction to ExpressJS

ExpressJS is considered a minimal as well as flexible web application framework of Node.js, which gives robust features for use of the web as well as mobile applications. ExpressJS is also considered an open-source framework, and it was developed and maintained by the foundation of NodeJS.

It also gives a minimal interface in order to make our applications. ExpressJS, in addition, gives us tools that are needed in order to build the app. ExpressJS is also flexible since there exist various modules that are made available on npm and that can be directly plugged into it, i.e, Express.

The developer of Express was TJ Holowaychuk and is currently been maintained by the Node.JS foundation as well as varied contributors of open source.

Why Should We Use ExpressJS?

Pug, which was earlier referred to as Jade, is a terse language that is used for writing HTML templates. It has various features as below :

• Pug produces HTML
• Pug supports dynamic code
• Pug also supports reusability (DRY)

It is one of the most popular template languages used with Express.

Rails and Django have got an opinionated manner of building up of applications that are its competitors. However, Express has got no way to do something since it is flexible and also pluggable.

Working with ExpressJS

We can install Express through NPM

npm install express

Now we’ll build a basic app using ExpressJS

• Navigate to the terminal and create a folder “Hello”

mkdir Hello

• Move-in the project & generate the package.json file by using npm init

cd Hello
npm init

•  Now Install express

npm install express –save

•  Now create a file server.js in the root using touch.

touch server.js

• Now all you have to do is paste the following code in the server.js file:

const express=require('express');
var app = express();
app.get('/', (req, res) => {
res.send('Hello Express')
});
app.listen(process.env.PORT || 3000)

Now, Let’s Understand What each line Means?

1. You can consider requiring to be a keyword to import something. We can instantiate it at the top of our file.

2. We have set the app variable to the creation of the express app.

3. Get implies that whenever it gets that route, it should always give the response which is mentioned in the function. It has 2 arguments:

• the URL
• the function telling express what to send back to the person who made the request

4. Listen well and bind the application to the port on your machine.

What Can you do With ExpressJS?

Request and Response objects of ExpressJS are parameters of the Callback function that is often used in applications of Express. The request object of express.js represents an HTTP request, and it also has got properties for the request query string, its parameters, the body, HTTP headers, and much more

Some generally used request object methods are as under :

• req.accepts (types): req.accepts is used so as to verify if specified types of content are acceptable or not, depending upon Accept HTTP header field of the request.
• req.get(field): req.get method task is to return the mentioned HTTP request header field.
• req.param(name [, defaultValue]): req.param task is to get the value of a param name whenever available.

Understanding

The middleware of ExpressJS is different functions that get invoked by the routing layer of ExpressJS before the final request handler. Just as the name specifies, it appears in middle between the initial request and the final route that is intended. Middleware functions in the stack are invoked in the sequence in which they are added.

It is usually used in performing tasks such as parsing the body for URL-encoded as well as JSON requests, and cookie parsing for the handling of basic and also building of JavaScript modules.

The most commonly used Middleware in the ExpressJS app.

• Application-level middleware
• Built-in middleware
• Router-level middleware
• Third-party middleware
• Error-handling middleware

Middleware functions are those which access the request and response object in the request-response cycle.

Middleware function Performs the Following Tasks

• Middleware function can execute any code.
• Middleware function can also make changes to request and response objects.
• Middleware function can also end the request-response cycle.
• Middleware function can, in addition, call the next middleware function in the stack.

Advantages of ExpressJS

ExpressJS has got many advantages which are as follows:

• It is a prebuilt framework of NodeJS helping us in the creation of server-side web applications in a faster and smarter manner.
• As Express is made in NodeJS, it inherits its many features like flexibility, scalability, simplicity, minimalism as well as performance.
• Briefly speaking, we can say that ExpressJS is doing things for NodeJS the same way Bootstrap is doing for HTML/CSS.
• Express also has made coding in NodeJS a piece of cake and also provided programmers with additional features so as to extend the server-side coding.
• ExpressJS, without any doubt, is the most famous framework of NodeJS in the way that when people are talking about NodeJS, they mean to say NodeJS + ExpressJS.

ExpressJS Scope

Scaffolding is a technique that is supported by some of the MVC frameworks. It is usually supported by the following frameworks :

• Ruby on Rails
• OutSystems Platform
• Express Framework
• Play Framework
• Django
• MonoRail
• Braille
• Symfony
• Laravel
• CodeIgniter
• Yii
• CakePHP
• Phalcon PHP
• Model-Glue
• PRADO, Grails, Catalyst, Seam Framework, Spring Roo, ASP.NET, and the list goes on.

It also tells programmers how application data should be used. This particular specification is being used by many frameworks that have got predefined code templates and also the generation of final code, which the application uses for CRUD operations (create, read, update, and delete)

Conclusion

Now after the discussion, we can conclude that we can create MVC web apps using ExpressJS. This framework is absolutely amazing for REST APIs too.

ExpressJS is also one among many well-known packages for use of NodeJS. It also is considered to be a web development framework that helps all of us in the development of great applications. It is also referred to as E in the MEAN stack and means stands for MongoDB, ExpressJS, AngularJS, and NodeJS. Also, the latest version of Express is Express version 4.0.0-rc1

Recommended Article

This has been a guide to What is ExpressJS? Here we have discussed the uses and advantages along with the scope of ExpressJS. You may also look at the following articles to learn more –

1. Express JS Interview Questions
2. What is CSS3?
3. What is API in Java?
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