react-logo

What is React?

React is a JavaScript library created for building fast and interactive user interfaces for web and mobile applications. It is an open-source, component-based, front-end library responsible only for the application’s view layer. In Model View Controller (MVC) architecture, the view layer is responsible for how the app looks and feels. React was created by Jordan Walke, a Software engineer at Facebook.

model-view
Fig: MVC architecture

Let’s take a look at an Instagram webpage example, entirely built using React, to get a better understanding of how React works. As the illustration shows, React divides the UI into multiple components, which makes the code easier to debug. This way, each component has its property and function.

instagram-components
Fig: Instagram Component

Now that we know what React is let’s move on and see why React is the most popular front-end library for web application development.


Why React?

React’s popularity today has eclipsed that of all other front-end development frameworks. Here is why:

  • Easy creation of dynamic applications: React makes it easier to create dynamic web applications because it requires less coding and offers more functionality, as opposed to JavaScript, where coding often gets complex very quickly.
  • Improved performance: React uses Virtual DOM, thereby creating web applications faster. Virtual DOM compares the components’ previous states and updates only the items in the Real DOM that were changed, instead of updating all of the components again, as conventional web applications do. 
  • Reusable components: Components are the building blocks of any React application, and a single app usually consists of multiple components. These components have their logic and controls, and they can be reused throughout the application, which in turn dramatically reduces the application’s development time.
  • Unidirectional data flow: React follows a unidirectional data flow. This means that when designing a React app, developers often nest child components within parent components. Since the data flows in a single direction, it becomes easier to debug errors and know where a problem occurs in an application at the moment in question.
  • Small learning curve: React is easy to learn, as it mostly combines basic HTML and JavaScript concepts with some beneficial additions. Still, as is the case with other tools and frameworks, you have to spend some time to get a proper understanding of React’s library.
  • It can be used for the development of both web and mobile apps: We already know that React is used for the development of web applications, but that’s not all it can do. There is a framework called React Native, derived from React itself, that is hugely popular and is used for creating beautiful mobile applications. So, in reality, React can be used for making both web and mobile applications.
  • Dedicated tools for easy debugging: Facebook has released a Chrome extension that can be used to debug React applications. This makes the process of debugging React web applications faster and easier.

The above reasons more than justify the popularity of the React library and why it is being adopted by a large number of organizations and businesses. Now let’s familiarize ourselves with React’s features.


Features of React

/react-features
Fig: React Features

JSX – JavaScript Syntax Extension

JSX is a syntax extension to JavaScript. It is used with React to describe what the user interface should look like. By using JSX, we can write HTML structures in the same file that contains JavaScript code. This makes the code easier to understand and debug, as it avoids the usage of complex JavaScript DOM structures.

jsx
const name = 'Simplilearn';
const greet = <h1>Hello, {name}</h1>;

The above code shows how JSX is implemented in React. It is neither a string nor HTML. Instead, it embeds HTML into JavaScript code.


Virtual DOM

React keeps a lightweight representation of the “real” DOM in the memory, and that is known as the “virtual” DOM (VDOM). Manipulating real DOM is much slower than manipulating VDOM because nothing gets drawn on the screen. When the state of an object changes, VDOM changes only that object in the real DOM instead of updating all of the objects. 

It may all seem a bit overwhelming for now, so let’s first understand what DOM is, and then we’ll go through how VDOM and real DOM interact with each other.

  • What is the Document Object Model (DOM)?
dom
Fig: DOM of a Webpage

DOM (Document Object Model) treats an XML or HTML document as a tree structure in which each node is an object representing a part of the document.

  • How do Virtual DOM and React DOM interact with each other?
virtual-dom
Fig: Virtual DOM

When the state of an object changes in a React application, VDOM gets updated. It then compares its previous state and then updates only those objects in the real DOM instead of updating all of the objects. This makes things move fast, especially when compared to other front-end technologies that have to update each object even if only a single object changes in the web application.


Performance

React uses VDOM, which makes the web applications run much faster than those developed with alternate front-end frameworks. React breaks a complex user interface into individual components, allowing multiple users to work on each component simultaneously, thereby speeding up the development time. 


Extensions

React goes beyond simple UI design and has many extensions that offer complete application architecture support. It provides server-side rendering, which entails rendering a normally client-side only web application on the server, and then sends a fully rendered page to the client. It also employs Flux and Redux extensively in web application development. Finally, there is React Native, a popular framework derived from React, used to create cross-compatible mobile applications.


One-way Data Binding

React’s one-way data binding keeps everything modular and fast. A unidirectional data flow means that when a developer designs a React app, they often nest child components within parent components. This way, a developer knows where and when an error occurs, giving them better control of the whole web application.

data-binding
Fig: One-way data binding

Debugging

React applications are easy to test due to a large developer community. Facebook even provides a small browser extension that makes React debugging faster and easier.

react-extension
Fig: React Extension

This extension, for example, adds a React tab in the developer tools option within the Chrome web browser. The tab makes it easy to inspect React components directly.

Now, let’s take a look at React’s important concepts.


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