Introduction to React JS 101

7 Minutes time to read

How to build a website? It is definitely not easy: it takes skills, knowledge, and tools to develop an effective web solution with a stunning user interface. Coding languages and libraries are essential to any web developer’s experience. With so many of them around, it’s hard to pick one that can create a high-quality platform that shows your expertise and modern approach to business.

One of the most popular frontend libraries is React JS. It’s an open-source component-based JavaScript library that creates highly flexible and responsive interfaces. If you haven’t heard of it, it’s time to get acquainted with it, and our React.JS development company has drawn a new guide that will help you to understand the essence of this tool better.

What is JavaScript

Before learning more about React and what a JavaScript library is, we should explore the nature of JavaScript. Right now, it is one of the most widely used web development tools that has a massive number of devoted followers and users. But what is it and how does it work?

It is a programming language that allows you to build dynamic web pages with various features – from simply adding the content of the website to integrating complex interactive solutions such as a hamburger menu, a user-activated color change, audio/video elements, sliders, all kinds of displays, and many more. 

To expand its functionality even further, developers constantly build new tools and solutions over it, such as APIs, frameworks, and libraries, such as React.

What is React JS

React is one of the most popular JavaScript libraries. It’s a front end open source tool that is perfect for building out flexible and user-friendly interfaces. It can also be used to create single-page applications or mobile apps. It allows to break down large pieces of the work scope into smaller ones with the possibility of scaling them up or down.

It allows developers to create reusable components and modify the data without reloading the page. As a front end tool, React works only on UI parts. However, its capabilities are endless, especially since it’s often used in combination with other libraries and frameworks. 

React JS history

React’s creation owes itself to the technical issue Facebook used to have with UX and website performance: as the application grew and became quite complex, it had to include dynamic UIs without compromising the speed. Finally, this problem was solved in 2011 by Facebook engineer Jordan Walke.

He chose JavaScript as a foundation for the library and used it in combination with XHP, a Facebook PHP extension. He and his development team released the solution, which instantly improved Facebook’s performance. It was later picked up by Instagram in 2012 and became open-sourced in 2013.

In 2015 the same team created React Native, which is a hybrid mobile app UI framework for iOS and Android. It is also becoming increasingly popular due to its feature-heavy functionality.

With the React JS definition and history unveiled, let’s get into why it is so popular among developers and what are the main pros of employing it.

Why use React JS

Before we start exploring React’s features more deeply, we should try to find out what exactly makes it so exceptional. Is it only the fact that it can create apps and websites of various complexity? Is it its open source nature? Its adaptability? Or is it a combination of those? Let’s get acquainted with the main reasons why React JS is worth trying out.

01 Component-based structure

The most obvious advantage of using React JS is that it allows you to break the page down into several components and modify them independently in any way your heart desires. You can update one of them without worrying too much about how it will affect the rest. It’s not an exclusive React feature but certainly one of the most crucial ones.

02 Flexibility

Since React is a library, not a framework, it’s much more flexible – there isn’t a system to master and a set of rules to follow. You can change it up and combine it with other applications and tools you’re used to. The level of flexibility and freedom it provides is unparalleled.

03 Easy to learn

One of the main reasons for React’s growing number of users is its simplicity. It’s easy to take up and learn, it doesn’t require very thorough knowledge. Basically, any JavaScript developer can pick it up and swing it, especially since it has a huge number of support forums and tutorials.

04 SEO-friendly

React doesn’t have a server-side rendering by default, but you can get around it by using necessary frameworks and add-ons. That allows React to create websites with astonishing speed and performance indicators which makes it incredibly Google-friendly. As a result, search engines scan your webpages much faster, thus increasing your chances of getting high rankings.

05  One-way data binding

React employs a downward data flow which means that data is passed down from parent components to their children but not the other way around. Changes in child structures do not affect the parent structures which makes the code much more secure.

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What is a JavaScript library

We’ve been throwing around terms like ‘library’ and ‘framework’ but what do they mean, and what is the difference between the two? For the most part, it’s purely theoretical. In a nutshell, the difference lies in this: a library is a reusable pre-written code that allows you to determine the project flow, while a framework provides the structure and determines the flow itself. Using a framework usually entails more coding and control and generally, it is more complex.

How is a JavaScript library different from other libraries? Essentially, the main difference is the role of JavaScript in the development process – if you’re used to working on JavaScript or if the project calls for it, using JS libraries is an amazing tool to expand the solution’s functionality.

We’ve talked about React’s definition, its nature as a JavaScript library, and what it can do but let’s focus on its main distinguishing features and explore them in detail.



Every web page consists of HTML documents that stipulate how these web pages are going to look. They are processed by browsers through Document Object Models (DOMs) as tree structures. If developers want to add or update something, they modify the DOM using languages like JavaScript.

In React’s case, it is done with the help of JSX – a JavaScript syntax extension that facilitates the process of DOM modification. JSX makes the code look simpler since it allows writing HTML-like code in React and is great at detecting possible errors in the code early on, which can be extremely useful on bigger projects. It is an optional element, but it can massively improve your React development experience.

Virtual DOM

What is the virtual DOM in React JS? Normally, whenever you change an element of a web page, DOM re-renders the whole set of components. If you use JSX, React JS creates a Virtual DOM – a copy of a website’s DOM that can’t change the content directly but can show what should be changed in the original DOM whenever a user action happens.

It re-renders the elements that were changed without reloading the whole page. In simpler words, React scans the Virtual DOM to see what happened after a said user action and selectively modifies the parts that need to be changed. That is an amazing tool that saves developers time and effort, which is especially crucial for dynamic and interactive pages with loads of updates and actions.

React Native

React JS operates extremely well on the web but not exclusively. With the help of React Native, developers can create native mobile apps. It means that they have a high-quality performance and access to the phone’s features and devices which makes the user experience more wholesome and profound.

React Native’s working mechanism is similar to the one of React JS: it is a JavaScript-based mobile app framework that builds UI blocks for iOS and Android. It doesn’t require developers to be proficient in native platform development – being familiar with JS and React is more than enough. It can potentially save a lot of time because they don’t have to learn a new language or framework to understand the code and bring fantastic results.

One-way data flow

We’ve touched upon this issue previously but let’s delve deeper here. React JS has a specific mechanism. In essence, it is quite simple: you define your component structure and hierarchy, fill it with components and relate each one of them to a specific element of your data model.

The data is passed via props – through a parent component to a child component. In React, a state is owned by one single component, which means that child components can’t alter the data that comes from their parent.

The main advantage of this mechanism is that you have more control over your code and you can see the errors and faults practically right away. It also helps to ensure a better performance since the data flow is clear, and you can always see all the pain points.

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React JS ecosystem

As you can see, React JS has a rather large and thriving ecosystem of supporting solutions and add-ons. Its community is growing every day and, thanks to its open source nature, developers polish it up and ensure it’s only improving.

The React JS ecosystem includes not only React, JSX, and React Native. It’s a collection of tools that cover some of the areas React JS can’t functionally cover. Let’s get acquainted with some of them.

01 Babel

Babel is a JavaScript compiler (or transpiler, to be exact) that transforms the code into a backward-compatible version that can be understood and processed by web browsers, for example, turning JSX into a “regular” JS code, or ECMAScript code to the standard version of JavaScript.

02 Webpack

Webpack is a static module bundler that scans all your modules, determines the dependencies, and compiles all your modules into one or several files based on those dependencies. It helps developers to not worry about the script order and possible errors and mistakes.

03 Redux

In React, components are the most crucial parts of the development process. They contain states (remember data about certain actions) which “inhabit” the components and urge them to re-render when something in the state changes. In larger applications, this might cause a problem that is solved by Redux. It is a state management system that allows you to store all the states in one place to ensure better tracking and control of the whole process which is vital for any development project.

04 Flux

Flux is an application architecture/pattern for React that helps to direct the data flow, overall data handling and ensures that the updates are made coherently and correctly. Basically, it supports the one-way data binding and makes it a default data handling way, and keeps all the data in stores. That’s crucial for scalable apps and complex solutions since tracking is becoming exponentially more difficult with the scope of the app.

Surely, there are hundreds of other tools and frameworks that support React JS and help developers to fully take advantage of its functionality. Let’s take a closer look at what constitutes React components and how they work within the system.

React JS components, props, and states

Judging by the name “component-based library,” we might guess that the most vital piece of React structure is a component. All of the React components are reusable and separate, which means that you can work on them individually without interfering with other elements. You can see the whole picture right away and pile the components together to form bigger clusters that will eventually turn into the final UI. 

Each component has specific attributes that are called props (properties). Props are used to pass the data around components. There is also such a thing as a state – an object that manages the component data internally. In simpler words, props allow components to receive the data from outside, whereas states help them to modify their own data within. The data from props cannot be changed by a component, while the state data can be modified internally.

There are two types of React components: stateless (functional) and stateful (class) components. Functional components don’t have a state – they accept the read-only data and return whatever they receive. Class components are called for whenever the state is needed. For example, when there is something dynamic or interactive going on since they track the information they get and work with other components.

Whenever the state changes via user action or setState( ) function, the DOM within the updated state gets re-rendered without re-rendering the whole application saving developers loads of time and nerves.

With React’s internal structure defined, its advantages unraveled – can we say that there are solutions that match their level?

What are React JS alternatives

After reading this text, you might think that React is a gift from developers’ heaven, but in reality, there are tons of other equally solid front-end tools that can cover most of the functionalities React provides. In the end, it is all a matter of preference for most of the projects. While React JS is extremely popular, there are several libraries and frameworks that are 100% on a par with it. 

– InfernoJS

A fine competitor to React, Inferno provides the same level of functionality, supports JSX, hyperscript, Redux, and is rightfully regarded as one of the quickest JavaScript libraries out there.

– Angular JS

You can’t find a better alternative to React than Angular. It has the same level of functionality to build rich and powerful SPAs for web and mobile apps. As React, it has loads of Angular-specific frameworks and tools that expand its technical abilities.

– Preact

Preact is the smallest React JS alternative, but its capabilities are definitely not that. There are few things to take into consideration: it doesn’t support a synthetic event system and is made out to be a React’s “clone”, which might be a hurdle for some developers. Why use a different library that resembles React if you’re already acquainted with React?

– Vue.js

Another decent competitor, Vue is extremely flexible and fast, allowing developers to build stunning web interfaces smoothly and super quickly. It has a large community, so learning the framework wouldn’t be a problem.

These are the most popular React JS alternatives, but there are many more, and the list doesn’t stop there. The beauty of the development process is that a lot of the time you can find a solution that fully fits your needs.

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On a final note

Building a website from scratch seems like an arduous task, but it doesn’t have to be. Right now, there are tons of tools, programs, languages, and solutions available on the widely used ones. React JS is definitely one of the best.

Its pros greatly outweigh its cons: it’s scalable, flexible, highly functional, and easy to get a grasp on. Its current popularity will attest to that: it is one of the most used web solutions. What is the future of React JS? We don’t know, but we for sure know that it’s not going down any time soon. 

If you still have any questions regarding this topic, make sure to contact us and bombard us with them – we know React JS in and out and will gladly help you to employ it and fix your website’s performance.

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