All About React.js: What It Is, How It Works, And Why You Should Learn It Now

Once upon a time, developers wrote huge canvases of code every single day. At some point, however, they realized that they were repeating many of its parts. From this, they concluded that it just wasn’t necessary to constantly reinvent the same algorithms. Instead, they chose to combine snippets of code into "packages", and use them as ready-made blocks — akin to a simple copy-paste. And that, ladies and gents, is how libraries and frameworks came on the scene.

One of the most popular JavaScript libraries, known as React.js, helps to create user interfaces. Its main task is to display pictures, text, buttons, etc. on the screen. The library is a Meta (Facebook) invention, and today every major company uses it to achieve its goals. But how does the “library of all libraries” work and why should you learn it? 

How React.js works

React.js resembles a Lego construction set: developers create reusable components from the main code. From these "cubes," they assemble different designs each time, or create several thematic sets - such as a car or a house - and use them as needed.

React.js also divides the page into components. This gives you ready-made code blocks, from which you can assemble the interface, a lot like using bricks to build a house. Components can include Facebook posts, profile info on a social network, or a block with the user’s photos.

Moreover, the components themselves include smaller ones: each post has a small user avatar, an author's name, a publication date, a block of text, etc.

React.js lets you define components as classes or functions. Beginners are advised to use the former, as they are more convenient for writing simple programs. However, React.js developers have improved their capabilities in the latest versions. This has led to functions being used more frequently by everyone and classes actively decreasing in usage. 

Class components do possess a wider functionality, and developers use them when they need to work with the state of the component, which we describe below.

A state is application data that can change. For example, a profile picture on a social network will appear differently on the profile page, in the header of the post, and the comments. When the component state changes, React.js starts rendering and updating the appearance of the page or application. 

React.js offers a very convenient way of working with a component’s state. For example, if you need to place a timer on a website,  React.js will automatically update it and display the correct time.

React.js components use a render method. This is the process by which React.js traces the components and requests an up-to-date description of each one. The description is made up of states, as well as random inputs called “props”.

You can compare this principle to making soup: you put vegetables, meat, and seasonings in a pot, and add water. Then you put the pot on the stove, and the rendering process - in this case, data processing - begins. When the soup is ready, you distribute it into bowls, and each person sees the same products, but in a transformed state.

Another feature of React.js is the use of a virtual DOM - or the Document Object Model - which is required for HTML to work. In regular JavaScript, updating the DOM is always done entirely, which noticeably slows down the page. The advantage of React.js is that it only updates the changed parts of the DOM, and skips the rest. To detect changes, React.js starts rendering, creates a virtual copy of the DOM, and compares it with the original. This process is called reconciliation.

React.js 101

To begin, you are required to master the basics of web development: JavaScript, HTML, and CSS. Only then can you transition to React.js, which uses JSX syntax - basically, a combination of HTML and JavaScript. 

Once you have a good command of the functionality and are fluent in React.js, you may already be considered a full-fledged front end developer! React.js is free and open source, which means that anyone can use, modify and share it with other developers.

React.js requires a description of "what" to do, not "how" to do it —  done automatically. This is called a declarative approach. It is very convenient for front end development since it is much easier to describe the final result than to give step-by-step instructions to achieve their goal. Examples of declarative languages include HTML and SQL. The opposite approach is called imperative programming.

The component approach that React.js uses emerged long before the invention of React.js itself. The developer community has already tested it on other projects and proved its convenience. Its advantage is that the components can be used multiple times (Just like Legos!) The developer doesn’t need to write code from the beginning every time, which helps save resources. React.js was invented by a software engineer at Meta. It is constantly updated, but changes happen smoothly and seamlessly for developers. 

React.js’s advantage lies in its versatility. It allows you to work with other libraries and frameworks, and develop websites, as well as all manner of web and mobile applications. Netflix, Instagram, Yahoo Mail, Airbnb, and The New York Times website, among others, are all written in React.js.

There are many additional extensions developed for React.js, which further simplify the work of the programmer. Here are some of them:

• React Style Helper: makes the style description in JSX easier. JSX is the programming language that React.js uses. It is a combination of HTML and JavaScript languages
• React Native: simplifies the development of applications created for a specific platform called Native
• Redux: another library used in conjunction with React.js that simplifies data transfer

React.js alternatives

Although React.js is very convenient and popular, there are many alternatives, since large companies adapt the code to fit their needs. Here are some examples:

• jQuery: focuses on the interaction between JavaScript and HTML
• Vue.js: a multifunctional framework that simplifies work with other libraries
• Angular: a framework from Google aimed primarily at creating SPA solutions, that is, single-page applications; requires implementation of components as classes
  

Why learn React.js

The first React.js release took place almost 10 years ago, and during its existence, a large community emerged. Today, it is one of the most popular libraries used by developers and is regularly updated. Many applications are written using it, and specialists who own this tool are actively sought out for work on a range of projects.

React.js is a repository of a huge number of elements and components — buttons, grids, labels; you can find anything you need for your project there. The library allows you to develop a complex website or application faster and easier, as well as structure and optimize existing code. In addition, React.js speeds up application deployment. 

React.js uses the JSX syntax, which is much more visual in nature than the JavaScript programming language. It is similar to HTML, but you can insert it into JavaScript code. This allows you to look at the structure and logic of the components inseparably. Besides, it makes it easier to make changes and fix errors in the code. And this, in turn, affects the speed of new releases and, concurrently, developer salaries.

Knowledge of React.js is a useful skill for those who already write in JavaScript, HTML, and CSS! It improves their knowledge and increases their market value as a developer. The salary of a React.js junior developer in the U.S. starts at $55,000 a year. Below you can see statistics from several job aggregators.

I want to learn React.js — where do I start?

Before you get started with React.js, you need to master the basics of JavaScript, HTML, and CSS. Learn how to apply them together, and only then should you try React.js. You will understand how the library functions and what scenarios it is best suited for.

One of the easiest and best ways to learn React.js is from the library website. It supports 17 languages, with nine more on the way. (Here is the complete technical documentation of the library!) You can also consult the developer community with any further queries.

What’s next?

The sky's the limit. With knowledge of React.js, you can progress in a variety of roles, learn other frameworks and libraries, and combine them with basic programming languages.

If you are interested in management, you can become front end team leader! In this case, you would be responsible for the distribution of tasks between programmers, coordination, and division of responsibility for the entire project, interaction with the customer, organization of training for new specialists, and so on.

It is important to understand that a team leader is more of a position than a profession, and should be occupied by a developer with broad competencies.

Ready to get started? TripleTen offers a convenient all-in-one solution for those who want to start their development journey — our Software Engineering Bootcamp! You will gain the knowledge and skills you need to move forward as a front end, back end, or full-stack developer.

Aside from your certification, the most important thing is building an impressive portfolio. TripleTen's Career Team can help you create a professional portfolio and feel confident throughout the hiring process. Visit the site to learn more about our top-rated bootcamp today!