What is ReactJS Introduction To React and Its Features

What is ReactJS? Introduction to React and its features

React JS is a popular JavaScript library, Developed by Facebook, it has brought a revolution to the front-end development world by providing a declarative UI for building applications using components.  Many believe that React JS is just some front-end library, but it’s actually more than that. ReactJS is a viewable javascript library created by Facebook that allows developers to create reusable UI components. In this blog, we are going to discuss the following points:

  • What is ReactJS?
  • Why we should use React JS?
  • Features of ReactJS
  • Types of Components in React JS
  • React JS VS React Native

What is ReactJS?

ReactJS is a JavaScript library for building user interfaces. React is an open-source JavaScript library for building user interfaces. It offers an alternative to traditional MVC-style web development architectures using a virtual DOM implementation. The initial release of React was in 2013 for use with the web browser but it now also supports native mobile platforms such as iOS and Android. Click Here to Get Started.

React’s creators call it declarative, but what they mean is “programmatically.” In other words, it lets you describe your application at a high level of abstraction, rather than a low level of code. This saves you from having to deal with all the plumbing details of data binding, event handling, and so on – details that are arguably the most important part of programming. And since your UI never changes, if you have a new app idea, all you have to do is write a new UI description instead of writing a whole new app from scratch. 

  • React is different from other JavaScript frameworks. It makes no assumptions about the rest of your technology stack, and is compatible with many different environments.
  • In fact, React can be used to build native mobile applications with React Native!
  • It gives you reusable components so that you can build complex web applications by composing simple parts.
  • It is open-source, free to use, and has a vibrant community support. It is used by some of the biggest technology companies such as Netflix, Airbnb, Dropbox, Uber, etc.

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Why we should use React JS?

  1. ReactJS is designed to be extensible, so it’s easy to add features in. It uses virtual DOMs, which means it’s faster and simpler than other frameworks. And it uses a virtual DOM diffing algorithm for updating elements, which means changes ripple through the entire application with no side effects.
  2. Easy creation of dynamic application: ReactJS makes it easy to build dynamic web apps with a lot of functionality. Because React is all about displaying data, you can create more sophisticated web applications with less HTML and less CSS.
  3. Improved performance: ReactJS allows you to create your web applications faster than conventional web applications. Any time data changes, all of its children are recomputed automatically. In addition to that, React is also a declarative library. It mostly avoids auto binding and callback functions in favor of props and state.
  4. Unidirectional data flow: In ReactJS, you have two things: components and props. A component is just a function that takes some inputs (props) and returns a description of what the UI should look like. The props are immutable values that describe a component’s configuration or state. When the props change, the component’s description of what the UI should look like changes as well. When a component receives new props because something changed in the parent component, it is re-rendered automatically without us having to do anything about it.
  5. Small learning curve is a small, quick learning curve. It’s not really about how much work it takes to learn something; what matters is how much you remember. If it takes three months to learn a new skill and you forget everything after three weeks, you still haven’t learned what you needed to.
  6. Easy tool for debugging: The first thing you learn about React is that it has a unique debugging system. Instead of the typical Web-page-like layout, it shows you a tree view, like a board game: an object’s state and its children all lined up side by side.

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Features of React JS

  1. JavaScript Syntax Extension: JSX is a new JavaScript syntax extension that brings the ease of HTML to JavaScript. It is similar to ECMAScript 6 but built on top of JavaScript. JSX is not a non-standard, but a JavaScript syntax extension that you can add to your code when you want to use it. It’s not a framework or a library or a framework for libraries. It’s a language extension that you can add to your code with a simple tag. The syntax looks pretty much like HTML and it works just like HTML. And because of its composability, it handles almost any situation where you need multilayered UI components in your app.
  2. Virtual DOM is a JavaScript object that is used for representing the current state of the DOM in memory.  React is fast. Really, really fast. The Virtual DOM gives us the ability to manage huge applications with no sweat at all. If you check out some of the plugins that allow you to see how performance is affected by the amount of the application you’ll notice an exponential curve which means that as your application grows your performance won’t drop as sharply as it would have with another library.
  3. Performance: React was designed for performance. It doesn’t use any of the tricks that slow down other JavaScript libraries like jQuery or AngularJS. And it doesn’t try to hide the DOM. Instead, it does what you would expect: it puts everything in plain JavaScript objects, so you know exactly how much work the program is doing. The only things React tries to optimize are properties that change very often, so if you keep changing them very often, you should probably use React.
  4. Extensions are what make React useful for building full-stack apps. They’re like plugins, but they’re implemented as React components. ReactJS components are like HTML elements (and like DOM elements, they can be nested inside other React components). You might think of them as the “React equivalent” to jQuery plugins. Because React depends on virtual DOM diffing, you must use fragments to keep track of what has changed and what hasn’t. But to keep track of changes in each component’s state that is not part of its render function, you can use life cycle methods to detect state changes and update state accordingly.
  5. One way data binding is a React concept that makes working with forms an absolute breeze. It allows you to display the result of a form in the view without having to write a single line of code. Let’s get started by looking at a simple example:
    • <form> <input type=”text” value={this.state.name} onChange={this.handleChange}/> <button type=”submit”>Add</button> </form>
    • This bit of code creates a form that accepts your name and allows you to submit it to the server. Nothing new here, just basic HTML. The interesting bits are in the render method:
    • Render() { return ( <div> <input type=”text” value={this.state.name} onChange={this.handleChange}/> </div> ) }
    • The handle change method updates the state when the user types in the input box, but we don’t have to do anything about it. React will update the view for us when this change occurs, which means that changing data or submitting forms will be as easy as adding or removing HTML tags.
  1. Debugging is considered essential by many developers because they provide helpful tools which are required to debug code in an easy manner. There are libraries available for debugging both in Node.js and browser.

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Types of Components in React JS

The React framework is composable. I can build an interface using React components that are built with other React components, and so on. This gives me a lot of flexibility in designing my interface because I can re-use components and build new ones as needed without having to alter the entire structure at once. This makes it easier to make changes. If I need to replace one component with another that does more or less the same thing but better, I can do so without breaking unrelated parts of my interface. Types of Components in React JS are described below:

Functional components

Functional components are a feature of ReactJS, which are fully aware of their environment, or in other words, are able to communicate with other components on the page. For instance, when you want to display a text inside a component, instead of writing <h1>Hi</h1>, you would write <Foo className=”bar”>Hello</Foo>. In this example, Foo is a functional component that would be rendered wherever there is a class Foo. In the code snippets given below, we have used some functional components as shown below:

<Foo name=”Babu” className=”baz” />

In these cases, both Foo and Bar are functional component classes. The <Hello /> component defines the Hello component class, and the bar attribute holds the string “Hello”. The following example shows how it works:

Let’s see how we can use a functional component in a website:

We will create two pages for our application – The welcome page and the About page. On the Welcome page, we will have a form with Name and Email fields where user can enter their details. On the About page we will have an image of the user along with his Name and Email fields. In order to show this image, we will use a functional component where we will pass data from the Welcome page as props to this component so that it can display it on the About page. We can see this in the following code snippet

< div id = “container” > < form > < input type = “text” value = “Enter your Name” /> < input type = “text


When you define a React component, you define two things: what the component should look like and how it should behave. This is called state. The above definition of reacting describes the state as “data that describes what the component looks like.” In other words, components are not only boxes that hold data; they also represent those data visually. This is not entirely accurate: React does not care about your data – it cares about how it is displayed – but we can learn something useful from this description.


React emphasizes “props” (properties) and “state” (inheritable values). Props are useful for passing data between components, and state is useful for maintaining information about the current view of an app. For example, if you’re using a component that expects a number as a prop but receives a string, you’ll get an error in development instead of something failing silently. That’s great! That’s why we have tests. And even if you don’t have tests yet, PropTypes will probably give you more confidence in your code when developing.

  • PropTypes are a new way to define the properties of a React component.
  • PropTypes are not part of the core React API. They are an optional part of React that can be used if you want stricter checks on your props or to report more helpful errors to your users.
  • Props are the inputs to components. They are controlled by the parent and they pass data down to the child. They can be strings, numbers, or even functions.
  • Often, we check our props right in the render function of the child component or use propTypes in class components because it’s easier to do that there. PropTypes allow us to check them right in the definition of components with type checks instead of doing string checks later.

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React JS VS React Native

The big difference between React JS and React Native is that React Native uses JavaScript but renders native components. On the other hand, ReactJS uses a Virtual DOM, which is a JavaScript representation of the actual DOM.

React JS VS React Native, which one to use? The most important thing is to decide on the environment where your app will work. This choice depends on a variety of factors, but the main ones are:

  • The existence of a native version of the application you need;
  • The extent to which the functionality of your application can be implemented with native components;

React JS also allows users to build reusable UI components. While in React Native, you usually use platform-specific UI elements like Button or TextInput.

  • With React JS, you get to use HTML tags directly in JavaScript which makes it easier to manage the layout of your application with CSS code. In the case of React Native, you need to use XML based language which makes it difficult for developers to customize the views if necessary.
  • React Native works best for apps that require multiple screens like games with levels or chat apps where you will be able to add new information on every screen refresh whereas, in the case of react js, interaction with users work via AJAX requests from web API


ReactJS is only one option among many when it comes to the front-end frameworks out there, but it’s certainly a solid choice. In fact, we think it’s a good idea to familiarize yourself with some of these different options and see which one fits your needs best.

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