There is a huge number of high-performing, real-time web applications being actively used by millions of internet users in the USA. Behind any sophisticated-looking graphical frontend application lies solid engineering known as the backend, which is responsible for processing data, performing security validations and communicating with servers. Traditionally, software developers had to acquire a completely separate skillset to effectively manage the frontend and the backend of a particular website. However, there has been an enormous paradigm shift in the software engineering field with the appearance of Node.js. With Node.js, software engineers get a tool allowing them to use JavaScript—a basic language of the web—in the backend.
It’s hard to underestimate the value of mastering server-side JavaScript for any aspiring web developer or software engineer considering working in the software roles in big American tech hubs like San Francisco, Austin, and New York. Node.js grew up from an innovative open-source experiment into a corporate-standard programming language, becoming the basis of digital infrastructures of huge enterprises like Netflix, Uber, LinkedIn, or Walmart. In this article, you’ll learn everything you need to know to start exploring the world of server-side JavaScript, including its architectural mechanics, basic setup, and request structuring, as well as the exact road map on how to become a backend developer after having knowledge of frontend design only.
Understanding the Architecture of Node.js
Before moving on to actual coding, you have to grasp the basic idea of how Node.js manages the information received on the server. The typical architecture of traditional web servers like Apache or Tomcat was based on the approach of creating a separate thread per each arriving request to process them. Though such approach proved quite productive in processing intensive computations, it was not scalable enough since any additional connections increased a need to allocate additional memory. That’s where Node.js came to life introducing a radically different concept of asynchronous, event-based architecture with a single thread running on Google’s lightning-fast V8 JavaScript engine.
The key innovation of Node.js is its ability to use the Event Loop to handle execution flow without any kind of interruptions or additional manual manipulations. Instead of suspending all of the current background activities for processing such operations as database querying or reading data from the local file system, Node.js offloads those heavy Input/Output (I/O) operations to the computer’s operating system directly. After that, the OS notifies the program of completion of the desired data gathering, adding a callback function into the execution queue and letting the Event Loop pick up the tasks to run them one by one without blocking the server or other users’ operations.
Unlike any other programming language, Node.js does not implement parallel execution with many threads. Its architecture is based on using one main thread that schedules long and potentially blocking operations asynchronously, guaranteeing maximum efficiency of the whole application regardless of the load. This approach provides certain advantages, but it makes developers think outside of the box, using such programming techniques as promises, async/await, or event handling.
Setting Up Your Professional Local Environment
To write backend code in JavaScript, you have to properly configure your computer or laptop to perform this activity. Go to the official Node.js website, and find there an appropriate version of Node.js installer for your operating system. You will have two version options—Latest Features and LTS (Long-Term Support). Always choose LTS version for serious learning purposes or when working professionally and for the production environment. Being maintained for several years, LTS provides high software stability, regular security patches, and no breaking changes in the underlying architecture of Node.js.
After installation of Node.js, you’ll get another useful utility called Node Package Manager or npm. Just imagine npm as an enormous online warehouse containing millions of pre-made code packages written and tested by other programmers. Without building entire software systems from scratch, you can use npm to download pre-made libraries like user authentication, email service integration, or data base management into your programs using a simple terminal command. After proper installation, you can validate correct implementation of the tools by printing version numbers using the following terminal scripts:
This script will print out version numbers for both Node.js and npm to validate their successful installation. Now, you’re ready to start building your very first backend project by creating a dedicated directory for it and initializing it with the terminal command npm init. The utility creates package.json—a structural file containing all essential metadata about your project and a list of all third-party libraries used in your project.
Building Your Very First Web Server with Express.js
Though Node.js provides an abundance of useful built-in core modules for implementing a web server, its syntax is sometimes difficult to handle, especially in complex logic scenarios. Because of that, Node.js-based backend applications rely heavily on various frameworks and utilities to simplify code and improve developer experience. One of the most prominent web application framework is Express.js. It is a light-weight web framework offering a simple and intuitive API to create web services with ease.
To start integrating it into your environment, you should launch npm and ask it to install this package in your local environment by executing npm install express. This command instructs npm to download necessary files and add it into the dependency list of your project’s package.json. Then, creating a server requires only several lines of code to be executed inside the application file.
After launching this file using the script node server.js, you’ll get a background daemon watching a particular port for web server communication. By entering an address of localhost on your web browser, the user opens a connection to your local server and initiates an HTTP request. Express.js detects this operation and finds an appropriate URL endpoint and processes the anonymous callback function associated with it, returning HTML string to render into your browser.
Understanding Basic Concepts of Server Routing, Requests, and Responses
In modern full-stack web applications, backend usually doesn’t have to deal with rendering static content. The sole purpose of any professional backend server is serving as a junction between client and permanent storage where data lives. All data processing and transfer is based on the architecture principle of REST (Representational State Transfer) APIs. According to the principle, client applications explicitly indicate their program intentions by using HTTP verbs for requesting particular data in the particular address of URL endpoint.
Basic HTTP verbs supported in REST are GET, POST, PUT, and DELETE. The GET request asks to fetch information from the server, POST request indicates that a new data record should be created, PUT request means updating already existing record with some changes, and finally, DELETE request means deleting a record. Express.js greatly simplified responses to these types of requests by offering a dedicated set of methods for dealing with each of them like app.get(), app.post(), app.put(), and app.delete().
To process the requests effectively, developers should parse three types of data coming from them. Firstly, Route Parameters are parameters directly included into URL of a particular HTTP request. Secondly, Query String is placed after ‘?’ symbol in URL, providing additional filtering or sorting options. Thirdly, Request Body is a large data record that needs to be posted into the database or used for creating new entities.
Database Connectivity and Data Persistence
A real-world backend application cannot live without the permanent data storage, which can hold all data in the long-run even after application server is restarted or shut down. Otherwise, if data is stored on server memory only, it vanishes immediately with restarting the service. If your goal is creating scalable applications capable of supporting thousands of concurrent connections, you’ll need to integrate your backend application with external database engine able to store data on physical disks of the hosting server.
The data inside databases usually comes either in the form of SQL rows organized in tables, or non-relational NoSQL objects. SQL databases like PostgreSQL or MySQL are perfect for finance-related applications that need to work with complicated relations between data elements. Meanwhile, NoSQL engines like MongoDB are more flexible and don’t require setting up table structures. Moreover, NoSQL databases are preferred by JavaScript programmers since data comes in JSON form, being compatible with standard JavaScript objects and arrays.
Integrating a database with backend application requires using a library that provides an ability to create and manage records. Typically, SQL databases are managed with help of so-called Object-Relational Mappers. As for NoSQL databases, developers use Object-Document Mapper (ODM). In MongoDB case, there is an advanced library called Mongoose, which lets you create a strict schema of database objects even in a case if it is not strictly defined.
Essential Middleware and Error Handling Strategy
When you’re building a real-world application, you will notice that there is always something common in several endpoints of your application. For example, you may want to log each request on terminal for debugging reasons, parse each request’s body, or validate whether the incoming request has come from an authorized user. But doing all these tasks inside a separate request handler function would violate the fundamental DRY principle of software engineering. Fortunately, this problem can be solved with help of middleware functionality implemented in Node.js.
A middleware is a special function run between two key points of request processing: when the server has received the packet, and the response is generated. It gets the request, response, and special method called next() that allows handing over the responsibility to the next middleware in the chain. Thus, you are free to write separate functions for parsing JSON data, managing CORS configurations, logging requests, or other activities related to each request.
One more key point you have to pay special attention to is your error handling strategy. While an uncaught error in a frontend application causes problems for a certain user, uncaught exceptions in backend code kill the whole server instantly. You have to ensure that any dangerous operation, like accessing the database or making HTTP requests to another API, will be wrapped with try/catch block, or there will be general Express error handler to catch errors.
Frequently Asked Questions (FAQ)
1. Is Node.js a frontend technology?
Absolutely not. Node.js is a runtime environment allowing to run JavaScript on backend of a web application, meaning that this code gets access to operating system, file system, networking libraries, etc. Unlike frontend applications, backend JavaScript can access system data independently from a browser and without the user’s permission.
2. Can I build my REST API using Node.js?
Definitely yes. Currently, creating APIs and microservices is one of the most common use cases for Node.js in the world of programming. Thanks to Express.js and other powerful web application frameworks, you can build extremely fast and scalable applications serving HTTP endpoints that accept or return JSON data.
3. Why big companies prefer Node.js over Python or Java?
Big companies use Node.js because of its excellent performance with high concurrency and ability to unify the software stack into a single language. Node.js asynchronous non-blocking I/O allows efficiently managing thousands of simultaneous connections with minimal hardware consumption. At the same time, Node.js allows easily sharing code between frontend and backend parts.
4. What is the difference between Node.js and Express.js?
Node.js is a programming language allowing running code on the server-side. Express.js is the name of a web application framework written in JavaScript and designed to simplify building server-side applications by handling request processing, data routing, and middleware integration.
5. What database should I study to start backend development in Node.js?
At first, you should familiarize yourself with the MongoDB database since this NoSQL database has a great compatibility with Node.js and uses JSON format. Later, you may want to learn PostgreSQL as a relation SQL database because it is used extensively in modern enterprise applications.
