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Overview Of ReactJS and Virtual-DOM

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( - What is ReactJS?

ReactJS is basically an open source JavaScript library that is used to build user interfaces specifically for single page applications. It is used to manage the display layer for web and mobile applications. React also allows us to create reusable user interface components. React was created for the first time by Jordan Walke, a software engineer who


works for Facebook. ReactJS implemented for the first time in the Facebook news feed in 2011 and in 2012.

React allows developers to create large web applications that can change data without reloading the page. The main objective of React is to be fast, scalable and simple. It works only in the user interfaces of the application. This corresponds to the visualization in the MVC model. It can be used with a combination of other libraries or JavaScript structures, such as the AngularJS in the MVC.

Who’s using React?

• Facebook
• Netflix
• Instagram
• Dropbox
• WhatsApp
• The New York Times

How does ReactJS work

Facebook recently launched ReactJS, an open source Javascript library, which benefited them in the development of some of its platforms, for example, Instagram. This library, despite having some controversial details, offers great benefits in performance, modularity and promotes a very clear flow of data and events, facilitating the planning and development of complex applications.

The secret of ReactJS to have a very high performance, is that it implements something called Virtual DOM and instead of doing the whole DOM in each change, which is what is normally done, it makes the changes in a copy in memory and then uses an algorithm to compare the properties of the copy in memory with those of the DOM version and apply the changes only in the variable parts.

This may sound like a lot of work, but in practice it is much more efficient than the traditional method, we have a list of two thousand elements in the interface and ten changes occur, it is more efficient to apply ten changes, locate the components that had a change in their properties and processed those ten elements, applied ten changes and processed two thousand elements.

How Does Virtual DOM Work in ReactJS?

Like the real DOM, the virtual DOM is a node tree that lists elements and their attributes and content as objects and properties. The render () method of React creates a tree of nodes from the React components and updates this tree in response to mutations in the data model, caused by actions. Since the underlying data is changed in a React application, the Virtual DOM representation of the user interface is created where things start to be interesting. Updating the browser DOM is a three-step process in React.

• Whenever something may have changed, the entire user interface will be rendered again in a Virtual DOM representation
• The difference between the previous and the new virtual DOM representation will be calculated
• The actual DOM will be updated with what actually changed. This is very similar to applying a patch.
The Virtual DOM is a deliberation of the HTML DOM. It is lightweight and confined from the program explicit usage subtleties. It isn't designed by React yet it utilizes it and gives it to free. Respond Elements lives in the virtual DOM.

They make the fundamental hubs here. When we characterized the components, React Elements can be render into the "genuine" DOM. Whenever a React Component is changing the state, diff calculation in React runs and distinguishes what has changed. And afterward it refreshes the DOM with the after effects of diff. The fact of the matter is - it's done quicker than it would be in the normal DOM.

Challenges or Limitation of reactJS

• ReactJS does not allow methods to be passed as additions so we can call a method that can change the state. We can not use the "State" value in the component function or function components written as a function
• Integration with some of the MVC structures would require a person to be aware of which configuration changes to pass
• Please remember that Each new CSS file created must be imported into reactJS. The extension of the files can be issued only for JavaScript files, all other files must be explicitly mentioned
• In the normal HTML attribute names are case insensitive, we have to be careful when using case insensitive names

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