Express is a free and open-source web application framework built on top of Node.js. Express is a tool that helps us set up routing and manage the request-and-response cycle. It is built on top of the Node.js built-in http module.
We construct server-side apps with Node JS, which is a fast JavaScript runtime environment. However, Node JS does not know how to serve files, handle requests, or handle HTTP methods. This is where express js comes in handy.
Express JS is a framework built on top of Node.js that aims to simplify the process of developing API-based online applications and cross-platform mobile apps in a short amount of time. Hence the importance of Express JS in Node JS applications os significant.
An overview of Express JS In Node JS
Writing Web applications is the most prevalent usage for Node.js, and a significant proportion of today’s web apps use Express.js as their server framework. [Case in point] Express is a tool that can be utilized in the development of JSON APIs, server-side rendered web applications, and microservices.
But how come? You won’t need Express if you want to use Node.js to build a simple HTTP server. You may accomplish this by making use of the http module that is built right in.
Express is described as a “Fast, unopinionated, simple web framework for Node.js” on the company’s official website. To put it in our own words, the process of constructing and maintaining a web server using Express (and the other web frameworks in the Node.js ecosystem) is considerably more user-friendly than doing it using the built-in Node.js tools.
Express makes use of these built-in utilities behind the scenes, but it also gives you access to a standardized set of handlers, settings, utilities, and other tools that vastly improve the user experience and the amount of time it takes to create a web server. The Express framework comes pre-packaged with the fundamentals of what you require to get started, and it does not impose any stringent limitations on how you must use the tools it provides in order to build your application.
The fundamental ideas behind Express.js In Node JS
The majority of web servers perform actions that are comparable to the following:
- Keep an ear out for any requests that could be coming in.
- You will need to parse the information that is supplied along with HTTP requests that you receive at an endpoint such as /home.
- Execute code in accordance with the HTTP verb that was used to make the request.
- In some way, respond to the request that was made.
When utilizing Express, we have access to tools that will assist us in completing these processes in a relatively little number of lines of code.
Express mostly operates with the following three major concepts:
- Routing:
The purpose of routing is to define what code has to be run in order to fulfill a request that was received by the server. In most cases, this is determined by analyzing both the URL pattern and the HTTP Method that is linked with the request.
If a GET request is received for the URL /home, for instance, the HTML for the homepage should be sent back. Create a new product listing if a POST request is received to the /products endpoint instead.
These are the fundamental components that make up any API or web service, and Express gives us with a variety of adaptable ways to construct code in order to manage these requests.
- Request/Response
When working with Express or any of the other Node.js server frameworks, you will constantly come across these concepts, which are sometimes abbreviated to req and res. They are symbolic representations of the Request that was submitted to the server and the Response that you will eventually send back to the server.
These are based on classes that are pre-built within Node.js. These objects are called Client Request and Server Response, and they are essential components of an HTTP transaction.
The Request and Response cycle is all that’s needed to represent a single HTTP transaction.
The server receives a request from one or more clients.
The server acknowledges receipt of the request and then reads the data that was sent along with it. This comprises the headers, the URL path that the request is being sent to, the HTTP method that was used to send the request, query parameters, cookies, the data or payload that was provided with the request (if any), and more.
A response must be sent from the server to the client. This must include a status code, headers, content encoding, any data that is being returned, and many other possible things.
The HTTP transaction is considered to have been finished once the server has sent the response back to the client.
This is a simplified example of what the Request/Response cycle looks like, but the interaction described here is at the heart of the vast majority of HTTP interactions.
Express assists us in concluding these transactions by advantageously enhancing the built-in Request and Response objects that the Node.js core http module offers whenever a request is received by your server. This module is provided by Node.js.
- Middleware
Middleware is code that runs at some point during the life cycle of the request/response cycle. It is most typically used to extend the capabilities of webservers or to modify their behavior.
Middleware is a term that refers to functions that can access the Request and Response objects. They are able to run any arbitrary code, and their execution is sequentially ordered according to the stacking order of the middleware components. The augmentation or addition of features to the req and res objects themselves is one of the most common ways in which middleware extends an application’s capabilities. Middleware is a component of the program that provides this capability. Your application can have middleware added to it without requiring a significant amount of code modification.
Express employs the Connect type of middleware, which is a format utilized frequently by Node.js server frameworks. That being the case, middleware developed for Express can also be utilized in a great number of other frameworks that provide Connect-style middleware.
To add functionality to an Express server, one of the most important things you can do is install middleware. The Request-Response cycle of your server can be enhanced with customisation and additional logic thanks to this pattern, which is both versatile and powerful.
And finally, a word about the Community
The community of developers who are using Express in production is the final component that contributes to Express’s remarkable capabilities. It is one of the most widely used server frameworks that can be combined with Node.js, and as a consequence, there is a great deal of information and material regarding it that can be found on the internet.
This is made abundantly clear by the vast number of middlewares that may be utilized to augment the capabilities of an Express application. Express makes extensive use of the modularity provided by the Node.js ecosystem, which places a strong emphasis on the use of building blocks known as modules.
When developing a web application using Node.js, Express is a good option to go with because it has a sizable community, a wealth of documentation, and plenty of expertise that has been put through the ringer and is easily available online.