Learn to Code with ReactJS

Published on:
December 22, 2023

React.js is a dominant front-end JavaScript technology that is quick, safe, and scalable. It offers an excellent user and developer experience.

What's more? Since Facebook and a thriving community support it, its popularity continues to rise. Azat Mardan writes in his book, “React is a robust UI library that provides an alternative that massive firms like Airbnb, Netflix & Facebook have adopted & see as the way forward.”  

According to GitHub, the amount of React.js package installations using NPM has increased dramatically in recent years compared to the other 2 renowned frameworks - Core/Angular & Vue. Technology adoption follows power laws, and React.js is dominating its category.

If you need help deciding which technology to use for your project, React.js is the best option. 

Let us tell you why! 

What is React js?

what is reactjs

React.js, or just React, is a JavaScript library for creating user interfaces. Every React web app comprises reusable components comprising various user interface elements. For instance, we may have a separate component for the menu bar, one for the footer, another for the main page & so on. 

These reusable components make development easier because we don't have to repeat repetitive code. You would need to write its logic and import the component into any area of the code that requires it.

Today, ReactJS is used by big shots like Facebook, Uber Eats, Dropbox, and many others, and it dominates over 40% of the web development market! 

Why choose React?

why choose reactjs

Many developers and companies have chosen React over alternative libraries/frameworks. Here are some reasons why:

  • Simple to learn: React is easy to learn and understand as long as you know the standards. React includes extensive documentation and a wealth of free resources from other developers online via React's thriving community.
  • Reusable components: Each React component has its logic, which can be used across the project. It saves the need to redo the same code many times.
  • Employment opportunities: At the moment, React is required for a higher percentage of front-end web development possibilities. So, knowing how React works and working with it improves your chances.
  • Improved performance: React's virtual DOM allows for faster page rendering. Using a routing package like React Router & have different pages rendered without reloading.
  • Extensible: React is a library that solely renders the user interface of our application. It is up to the developer to decide which tools to use, such as libraries for rendering various pages, design libraries & so on.
  • SEO Friendly: ReactJS can improve search engine optimization (SEO) by boosting web application performance with Virtual DOM. Also, by performing server-side rendering, React can help search engines navigate web applications easily. 

Features of ReactJS

ReactJS is an exceptional JavaScript framework for web developers because it is significant in the front-end ecosystem. But what makes React stand out from others? 


This JavaScript syntactic extension expands the ES6 (ECMAScript 2015) features. You can now integrate JavaScript functionality and markup in a component. Creating a template in React using JSX is easy, but it is not a simple template language; it incorporates all of JavaScript's features.

Here's an example of a code block that demonstrates how to incorporate an expression in JSX:

const name = 'John Smith';
const element = 

Hello, {name}

; ReactDOM.render( element, document.getElementById('root') );

In the second line, we use curly brackets to call the name variable inside a React element.

The ReactDOM.render() feature depicts the UI by rendering the React element on the DOM - Document Object Model tree.

Virtual DOM

It is a copy of the DOM object that refreshes and re-renders our pages when modifications are made; it then compares the current state to the original DOM to keep it in sync with the modifications. This results in faster page rendering.

Components & Props

ReactJS separates the user interface into independent, reusable pieces of code known as components. React components, like JavaScript functions, accept arbitrary inputs called properties or props. The returned React elements determine the client-side UI. Here's an example:

function Welcome(props){

Hello, {props.name}


Having as many components as you need without clogging up your code is possible.

One-way Data Binding

One-way data binding means a single data flow. Data in React flows in one direction, from top to bottom, from parent to child components. The attributes of the child component cannot return data to its parent component, but they can interact with it to modify the states based on the inputs. 


With React.js, the code centers on what is displayed rather than how it should be displayed. This method is also faster for creating and debugging a screen or component. Declarativeness implies excellent DX (development experience), which frequently correlates to excellent UX. As Artemij Fedosejev writes, “React wraps an imperative API with a declarative one. React’s functionality is based on how it makes you create code.”


React.js is lightweight and quick to download. Configuring the programming environment is relatively easy. Furthermore, with the code-splitting feature, you don't necessarily have to load the complete application, which can considerably cut the load times of your website or web app. Because Google supports sites with low loading times, smooth and fast loading times are critical for the UX of your product and marketing.

Backward Compatibility

It is always beneficial for software to work with earlier versions of the libraries on which it relies. However, because it is costly, only some frameworks & programming languages can offer backward-compatible features.

State Management

A "State" is a JavaScript object that embodies a component's current status. It stores and manages dynamic data such as user input, server answers, etc. Today, there are many state management frameworks available, but Redux and Recoil are two of the most popular.

Vast Community

React has a huge and active developer community that contributes to the project by creating complementing tools and libraries.

ReactJS vs. React Native

Although React Native and React are fairly similar in their foundation, they have some significant differences. When ReactJS renders code using Virtual DOM, React Native is a framework that functions as a bridge & runs components using exclusive native APIs. 

React Native, as opposed to React, addresses the requirement to create distinct code for different platforms and design apps that adhere to platform-specific UI and UX principles. As developer Kingsley Ubah says, “React DOM uses HTML, CSS, and JavaScript for layout styling & enables developers to build interactive UIs. On the other hand, React Native uses native UI components & APIs to develop cross-platform mobile apps.

Getting Started With React

Now that we have cleared the basics, it’s time to know how to start with React.


Before using React, you should be familiar with and comfortable with JavaScript. Before utilizing React, you recommend brushing up on several JavaScript topics, like:

  • Arrows function
  • Rest operator
  • Modules
  • Array methods
  • Keywords

Besides, you should also be familiar with HTML, as the markup is used in the JSX syntax.


Next comes the installation part. Before setting up React, you need to have Node.js installed on your machine. Once you've successfully installed it, type the following command into your terminal:

node code

Now install React by running the following command. But before that, create a folder where you’d like your app installed.

node code

Here, it’ll be installed in react-kit. When the setup process is complete, go to your favorite code editor and start coding! 

Learning Components

React offers two types of components- class components and functional components. Most components return HTML code with a combination of dynamic JavaScript values and are built similarly to functions.

React Class Component

Let's look at an example of a React class component. Ensure that the React. The component statement and the render() subclass are present in every component.

class Student extents React.Component {
    constructor() {
        this.state = {language: "JavaScript"};

I am learning {this.state.language}

} }

Here, we defined a state variable called a language with the string value "JavaScript," which was then used in the markup. It shows how JavaScript and HTML can be combined without DOM techniques. If we send it to the browser, it will display "I am learning JavaScript" on the page.

React Functional Component

Next, let’s look at a functional component with the same example.

function Student(){
    const language = "JavaScript";
    return (

I am learning {language)

); }

Components always start with a capital letter, as we have done here with Student. Like the above example, this variable was used in the markup without manipulating the DOM.

Handling Events

The events used in React are the same as those used in HTML. But in React, events use camelCase syntax, meaning "onclick" would be "onClick," "onchange" would be "onChange," and so on. We use curly brackets to pass an event as an attribute in an HTML tag: onClick={changeName} instead of quotations. Let’s look at an example.

import {useState} from "react";
function App() {
    const [name, setName] = useState("John");
    const changeName = () =>{

His name is {name}

); } export default App;

The defined function here displays a message in the browser. When clicked, the button sends the message using the onClick event handler.

Working with States and Hooks

In React, we use a Hook called the useState Hook to manage the state of our application. Hooks allow us to access more React capabilities without writing a class. Hooks allow us to manage our component's state and even conduct specific effects when our state variables are rendered for the first time or updated.

If we don’t use the useState Hook in a functional component, no changes made will be reflected in the DOM, resulting in the state remaining unchanged.

Let's take a look.

import {useState} from "react";
function App() {
    const [name, setName] = useState("John");
    const changeName = () =>{

His name is {name}

); } export default App;

First, we imported the useState Hook and added a state variable “name” and a function “setName.” Initially, the useState Hook stores the name"John."

Then, we used the function called changeName, which uses the setName function to update the value of the name variable. When we clicked the button, "John" changed to "James" in our markup.

React Hooks

React Hooks are basic JavaScript functions that separate reusable and functional components. Hooks can be declarative & monitor various issues.

React offers several basic built-in hooks:

  • useState: It can administer states, returns a stateful value & an updater function to keep it current.
  • useEffect: It manages side effects such as API requests, subscriptions, timers, mutations, and other events.
  • useContext: It returns the current value of a context.
  • useReducer: An alternative to useState for complicated state management.
  • useCallback: It returns a memorized version of a callback to assist a child component in not having to re-render itself.
  • useMemo: It returns a memoized value that can be used to optimize performance.
  • useRef: It returns a ref object with the .current property. The ref object can be modified. It is primarily used to access a child component forcefully.
  • useLayoutEffect: It is executed at the end of all DOM modifications. Using useEffect over this one is preferable, as useLayoutEffect fires synchronously.
  • useDebugValue: Allows a label to be displayed in React DevTools for custom hooks.

Besides, you can also write custom hooks for specific use cases such as data retrieval, logging to disk, timers & more. So, relax the next time you come across React Hooks in a codebase or are required to develop one. It's also a JavaScript function for maintaining the state & side effects of functional components.

Routing in React

In ReactJS, routing is the technique that allows us to move through a website or web application. Server-side routing and client-side routing are two types of routing. React Router, on the other hand, is a component of client-side routing. 

Without knowing anything about React Routing, you can manually construct it using useState and JSX for conditioning. Even though it is inefficient for large-scale applications such as e-commerce, it can still be used as a boilerplate for learning routing and as a framework for React JS routers.

For example,

const[page, setpage] = useState("products") const routeTo = (newpage) =>{ setpage(newpage) }

React Router allows us to explore the components and create a single-page application without reloading the page as the user navigates, resulting in an effective UX experience. Browser Router or React Router API is a popular library for React routing that allows you to move between different components in a React application while keeping the UI in sync with the URL.  

The official react-router documentation says, "React Router is a fully-featured client and server-side routing library for React, a JavaScript library for building user interfaces." 

React Routing is available in three packages.

  • react-router: It’s the core region of react-router, offering essential routing features in web apps, including all react-router-dom & react-router-native packages.  
  • react-router-native: It is used in mobile applications to route traffic.  
  • react-router-dom: It is used in web applications to implement dynamic routing.

These routers further allow 3 types of ReactJS routing:

  • Browser Router - It’s regarded as the famous & highly used router with HTML5 history API (replaceState, pushState & the popstate event) to position your UI in sync with the URL. 
  • Hash Router - As the name suggests, this router has the hash URL component to maintain your UI in sync with the URL.
  • Memory Router - A router that knows the history of your "URL" but won’t reflect in the address bar—frequently used in testing & non-browser workspaces such as React Native.

ReactJS Use Cases

So far, we have discussed everything about React. Now, it’s time to look at its many use cases.

Today, ReactJS is used by many bigshots like:

  • Social Network Apps (Facebook, Instagram, Pinterest, and Twitter)
  • Share economy services (Airbnb, Lyft, Uber)
  • SaaS applications (SendGrid, Asana, InVisionApp, and Zapier)

But that’s not all. The list of ReactJS use cases is endless, but here are some examples. 

  • Business websites
  • Portfolios
  • Forums
  • E-learning modules
  • Galleries
  • Job boards
  • Q&A websites like Quora
  • Media-centric sites like YouTube & many more! 

In a nutshell, React can be used to create any digital product that runs on the web! 


ReactJS is a powerful JavaScript library used to construct dynamic web applications. It, among other things, streamlines JavaScript writing and improves the performance and SEO of your application.

Using one-way data binding, ReactJS helps speed the debugging process and decreases the possibility of errors. As Artemij Fedosejev writes in his book - React.js Essentials, “React brings profound ideas on how to work with the DOM, manage your application’s data flow & imagine UI elements as individual components.”

When it comes to development, React has it all. ReactJS is gradually overtaking its competitors, Vue.js and Angular, as the preferred framework for building web apps among developers. So, whether a beginner or an experienced developer eager to advance, learning ReactJS can become a highly sought-after skill! 

Want to start your new project with React? Reach out to MarsDevs. Book a slot today with us! 


  1. Why is ReactJS widely used?

Because of its increased simplicity and versatility, ReactJS has surged in popularity in recent years. The phrase "future of web development" is often used to characterize it.

  1. How many Hooks are in React?

Hooks allow you to write less code in React. React 18 has 15 hooks for developers. With 15 hooks, you may accomplish functionality similar to a class-based component.

  1. What is the smallest block of ReactJS?

Elements are React apps' smallest building blocks. What you want to see on the screen is described by an element: const element = <h1>Greetings, world</h1>. 

  1. What problem does ReactJS solve?

At its foundation, React is a solution to a problem that developers face when developing user interfaces. Developers can use it to construct complex user interfaces with frequently changing components without writing plenty of difficult JavaScript code.

  1. What is the lifecycle method in React?

Components in React have a lifespan that is divided into phases. Every stage has a set of lifecycle methods invoked at various stages throughout the component's lifecycle. These methods enable you to control the component's behavior and conduct particular actions at various points in its lifetime.

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