Express JS

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Introduction to Express JS

Express JS is a minimalist web framework for Node.js that allows developers to create web applications and APIs easily and efficiently. Unlike other more complex frameworks, Express focuses on providing a basic yet powerful set of tools to handle HTTP requests, routes, and middleware. Its simplicity makes it one of the most popular choices for backend development with JavaScript.

What is Express JS?

Express JS can be described as a thin layer built on top of Node.js that facilitates web server development. Without Express, Node.js is fully functional, but many of the tasks a web developer needs to do, such as handling routes or managing middleware, require additional code. Express abstracts those tasks and allows for a more efficient workflow.

History and Evolution

Express was created in 2010 by TJ Holowaychuk as a lightweight and modular solution for development with Node.js. Over time, it has evolved to become one of the most used frameworks by backend developers, being a fundamental pillar for applications ranging from simple websites to complex and scalable systems.

Installation and Getting Started

To start working with Express, we first need to have Node.js and npm (Node Package Manager) installed on our machine. Once we have these tools, we can install Express in our project.

Installing Express

To create an Express project, the first step is to initialize our project with npm and then install the framework.

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"First, we create a folder named my-express-app and move into it. Then, we initialize an npm project with the command npm init, using the parameter -y to accept the default options. Finally, we install Express with npm install express."

Once Express is installed, we can begin configuring our basic application.

Creating a Basic Application

Next, let's see how to create a basic Express application that responds to HTTP requests. To do this, we will create a file app.js that will contain our main code.

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"In this code, we first import Express using require. Then, we create an Express application instance with const app equal to express. After that, we define a route with app dot get, which listens to requests on the main route, the slash. This route responds with the text Hello World. Finally, we set up our server to listen on port three thousand."

By running this code with the command node app.js, the server will be running, and we can access the application through http://localhost:3000.

Middleware in Express

One of the most important features of Express is the use of middleware. Middleware is a function that has access to the request object (req), the response object (res), and the next function, which indicates when to pass control to the next middleware.

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"This is an example of a simple middleware that logs the time of each request to the server. The middleware receives three parameters, req, res, and next. The next function is called to let the application flow continue to the next middleware or route."

Middleware is a key tool in Express for adding features such as authentication, validation, or error handling to each request.

Conclusion

Express JS is a framework that greatly facilitates backend development with Node.js by providing powerful yet simple tools to handle HTTP requests, routes, and middleware. In this chapter, we have seen how to install and configure Express, as well as create a basic application.

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