What is Express.js? Everything you need to know (2023)

Express.js is the most popular backend framework forNode.js, and is a big part ofecosistema JavaScript.

Designed for building hybrid single-page and multi-page web applications, it has also become the standard for building back-end applications using Node.js and is the back-end part of something known as the MEVN stack.

MEVN is a free, open-source program.JavaScriptSoftware stack for creating dynamic websites and web applications with the following components:

  1. MongoDB: MongoDBGenericNameis the default NoSQL database
  2. Express.js:The standard web application framework for building web applications
  3. Vue.js:The progressive JavaScript framework used to buildFront-end web applications
  4. Node.js:JavaScript engine used for scalable server-side and network-side applications.

This guide explains the main features of the Express.js framework and how to create your first application.

What is Express.js?

Express.js, sometimes called "Express", is a minimalistic, fast, Sinatra-like Node.js.Marco de Back-Endthat provides robust features and tools for developing scalable back-end applications. It provides the routing system and simplified functionality to extend the framework by developing more powerful components and parts based on the application's use cases.

What is Express.js? Everything you need to know (1)

The framework provides a set of tools for web applications,HTTP requests and responses, routing and middleware to build and deploy enterprise-grade applications at scale.

It also provides a command line interface (CLI) tool calledNode-Paketmanager(NPM) where developers can have packages developed. It also forces developers to follow the Don't Repeat Yourself (DRY) principle.

The DRY principle aims to reduce the repetition of software patterns by replacing them with abstractions or using data normalizations to avoid redundancies.

What is Express.js used for?

Express.js is used for a variety of things in the JavaScript/Node.js ecosystem: you can develop applications,API Endpoints, routing systems and frameworks with it.

Here's a list of some types of apps you can build with Express.js.

Single Page Applications

Single Page Applications (SPAs) are the modern approach to application development where the entire application is directed to a single index page. Express.js is a great framework for building an API that connects these SPA applications and serves data consistently. Some examples of single page apps are Gmail, Google Maps, Airbnb, Netflix, Pinterest, Paypal and many others. Businesses use SPA to create a seamless and scalable experience.

Real-time collaboration tools

Collaboration toolsThey're here to facilitate the way businesses work and collaborate every day, and Express.js makes it easy to build real-time collaborative network applications.

In addition, the framework is used to develop real-time applications such as chat and dashboard applications where it is easy to integrate WebSocket into the framework.

Express.js handles the routing and middleware part of the process, allowing developers to focus on the critical business logic of these resources when building tools for live, real-time collaboration.

(Video) What Is Express JS? | Express JS Tutorial for Beginners 2022 | Express JS API | Simplilearn


Streaming applications like Netflix are complex and have many layers of data streams. To develop this application, you need a solid framework to handle asynchronous data streams efficiently.

It is an ideal framework for building and deploying scalable, enterprise-grade streaming applications.

Fintech Applications

Fintech is computer software and other technology used to support or enable banking and financial services. A fintech application is currently being createdindustry trendand Express.js is the framework of choice for building highly scalable fintech applications.

If you want to build a fintech app with a large number of users and transaction volume, join companies likePayPaland Capital One to develop and deploy their application using Express.js.

Why you should use Express.js

There are a number of reasons why you should consider using Express.js in your next project, from faster I/O for faster requests and responses to its single-threaded system and asynchronous processes. It also uses the MVC framework to simplify data manipulation and routing systems.

Let's take a look at some of the top reasons you should consider using Express.js.

agile and fast

Express.js is very easy to use, flexible and faster than any other Node.js framework. A minimalist framework provides rapid application development and relieves the stress of mastering the different parts of a larger framework. It also offers advanced features like an excellent routing system, middleware, and out-of-the-box content negotiation.

Part of the MEAN file

Express.js is the framework of choice on any stack, represented by the E on any stack, such as B. MERN, MEAN, etc. It can also be easily integrated into any stack or technology to show how important the framework is in the MEAN stack development process.

In addition, it can be efficiently connected to a more robust database management system than the traditional one.MySQLand provides a continuous development process for each stack. This combination of features makes Express.js very popular among MEAN developers.


Express.js has proven to be very scalable over the years, with many large companies using the framework on their servers on a daily basis.

It handles user requests and responses efficiently and requires little to no additional configuration when developing a rich web application.

It has great additional modules, packages, and features that help developers create reliable and scalable web applications.

Compatible with Google V8 engine

Express.js is compatible with many Google V8 engine packages, making it a very powerful framework for building and deploying enterprise-level, real-time, collaborative, and network-based applications.

The Google V8 engine is a powerful, open-source JavaScript and WebAssembly engine that supports high speed and scalability for complex and intensive applications. Having packages that use the Google V8 engine is a huge performance and scalability boost for your backend application.

(Video) Learn Express JS In 35 Minutes

community support

As the framework is the most popular Node.js backend framework, it offers the most community support, features, and packages for all development challenges. Google support is also extensive, making the framework a popular choice among Node.js developers. Its open-source nature gives developers the ability to create extensible packages and resources to make development easier, not just for them, but for anyone else programming with Express.js.

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Powerful routing system

The framework has the most powerful and robust out-of-the-box routing system to help your application respond to a client request through a specific endpoint.

The routing system in Express.js allows you to break down your bloated routing system into manageable files using the framework's router instance.

The fast routing system is useful to manage your application structure by grouping different paths into a single folder/directory.

Developers create more maintainable code by bundling functionality with the express router and avoiding duplication of effort.


Express.js is a framework that includes a set of middleware to create a continuous development process.

Middleware is code that runs before ahttp requestIt hits the route handler or before a client gets a response, giving the framework the ability to run a typical script before or after a client request.

With middleware, developers can inject scripts to intercept the flow of the application; For example, developers can use the middleware to verify that a user has logged in or out correctly.

(Video) Learn Express Middleware In 14 Minutes

How Express.js works

Because Express.js uses the client-server model to accept user requests and send responses back to the client, it doesn't work that differently from other popular frameworks.wie man laravelt, working alone.

When a user sends a requestfrom the web browserEntering the address of a website causes the browser to send an HTTP request to the application/server (many applications built with Express.js arehosted somewhere in the cloud).

The server receives the request for one of its routes and processes it using the controller that corresponds to the requested route.

After processing, the server sends a response to the client.mit HTTPsince it is a round-trip communication protocol.

The response returned to the client can be plain text, a dynamic HTML page that the browser renders and displays a responsive web page, or JSON data that the browser providesFrontend Developerwill be responsible for the display of information on the website.

Let's create a simple server to monitor incoming requests for a specific oneURLand port number with Express.js:

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const express = require('express')const app = express()const port = 4000app.get('/', (request, response) => { response.send('Testing Hello World!')})app.listen (porta, () => { console.log(`Testapplikation auf http://localhost:${port}`)})

This is a simple Express.js server listening for incoming requestshttp://localhost:4000/and give a text reply of "Trial Hello world!“.

How to create an Express.js application

Now let's create a real demo application using the new Express.js 5.0. First create onedirectoryfor your new application and install the following packages:

mkdir first-express-appcd installs primero-express-appnpm[email protected]--ointment 

Then create an index.js file in the root directory and paste the following:

toque index.js

After configuring the server as shown above, let's create oneEverythingArray containing all of our pending tasks to return to the user depending on the endpoint called.
Add the following codeindex.jsFile, archive:

const express = require("express");const app = express();const port = 3000;app.listen(port, () => { console.log(`App testen, die auf http://localhost :${ lauscht port}`)})const todos = [ { title: "Todo 1", desc: "This is my first Todo", complete: true, }, { title: "Todo 2", desc: "This is my second Todo ", complete: true, }, { title: "Todo 3", desc: "This is my Third Todo", complete: true, }, { title: "Todo 4", desc: "This is my four Todo", done: true, }, { title: "Todo 5", desc: "Das ist meine fünfte Todo", done: true, },]; // Quelldaten enden hier

Next we create an endpoint to fetch all of themEverythingstored on our server:

(Video) Node.js + Express - Tutorial - What is Express? And why should we use it?

app.get("/all", (request, response) => {response.status(200).json(all);});

Then a point to retrieve a singleAllrelated toI WOULD GOOf the whole:

app.get("/all/:id", (request, response) => { response .status(200) .json({ data: all.find((all) => all.id === request.params .yo würde) });});

Now an endpoint to store a new oneAll:

app.post("/all", (request, response) => { all.push(request.body); response.status(201).json({ msg: "All created successfully" });});

Then a final point to update an existing oneAllI likeI WOULD GO:

app.put("/todos/:id", (Anfrage, Antwort) => { const todo = todo.find((todo) => todo.id === request.params.id); if (todo) { const {title, desc, complete} = request.body; all.title = title; all.desc = desc; all.completed = complete; response.status(200).json({message: "Everything updated successfully"} ) ;return; } response.status(404).json({ msg: "All not found" });});

Finally, we create an endpoint to remove a single oneAllrelated toI WOULD GO:

app.delete("/todos/:id", (request, response) => { const todoIndex = todos.findIndex((todo) => (todo.id = request.params.id)); if (todoIndex) { todo.splice(todoIndex, 1);response.status(200).json({ msg: "Everything removed successfully" });} response.status(404).json({ msg: "Everything not found" }) ; });

This code snippet shows how to implement a DELETE function in Express.js. Captures the todo id via parameters, searches the array for the matching id and removes it.

Express.js application test

Now it's time to try our new Express.js application!

Run the following command to test our newly developed REST APIpostmanand make sure we have the correct data:

sin index.js

You can download Postman from the official website and try the test below. Done, for more information we encourage you to build more functions using the approach discussed in the article and expand your knowledge of Express.js

What is Express.js? Everything you need to know (2)

Keep going

Express.js is the most popular framework in the Node.js ecosystem, and it's not hard to see why. It offers a variety of benefits and features that you can take advantage of.

Express.js' flat learning curve makes it very easy and simple to get started. It abstracts unnecessary or unwanted web application functionality and provides a thin layer of core functionality that allows for flexibility.

Since the Express.js framework forms the basis ofNode.jsKnowing Express.js will automatically give you a decent understanding of other popular frameworks. This knowledge can help you make important decisions about building business logic, what framework to use other than Express.js, and when to use standard or custom packages.

What do you plan to develop next with Express.js? Let us know in the comments section.

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(Video) What is Express JS? | Explained in 3 min

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