What is ReactJS Introduction To React and Its Features

What is ReactJS? Introduction to React and its features

React 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 ReactJS 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.

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What is ReactJS?

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. Click Here to Get Started.

Why ReactJS?

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.

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.

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.

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.

Small learning curve

A 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.

It can be used for the development of both web and mobile apps

React was created with the purpose of making it easier for developers to develop native mobile apps using pure JavaScript. Thanks to its use of a virtual DOM, React allows developers to make changes to their code at any time without having to rebuild anything. However, there are a few drawbacks. For example, React does not have a built-in event system or an option for building reusable UI components that can be used in multiple apps or websites.

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 ReactJS

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.

Virtual DOM

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.


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.


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.

One way data binding

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.


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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Components of ReactJS

Components are the building blocks of React.

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.

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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.

ReactJs prerequisites

  • Knowledge of HTML
  • Concepts of programming
  • Basic knowledge of JavaScript

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