Is React JS fast? When creating volumetric applications with complex logic and an abundance of animated elements, the issues of performance become critically important. That is why, when choosing a particular framework, we always strive to find the option which will allow creating the most responsive application in full accordance with user’s requirements. Among the most functional and rapidly developing, two instruments are often named the most efficient – the ReactJS library and its direct competitor, full-fledged AngularJS framework. In this article, we will try to answer why we consider React JS faster than Angular, and, in particular, review the factors that help achieve the highest possible performance.

Why Is React JS Fast? Virtual DOM

Answering the question: “is React JS fast?” we should mention one of the main features of ReactJS – virtual DOM. Let us figure out how it can speed up the application. To do this, we must first find out the principles by which the normal (real) DOM operates.

Real DOM – Document Object Model, is an abstraction of the application structure, represented as HTML text with embedded script modules in the memory of the carrier device. In fact, the DOM itself is updated quickly enough; its redrawing is similar to the one that occurs with JS objects. However, it is not designed to be used with modern dynamic UIs.

For example, leafing through the news feed in social media, we may need to refresh tens of thousands of nodes. One such manipulation in the case of real DOM will take at least 1 second, which by the current internet standards is a monstrously slow rate. From a technical point of view, the rendering process consists of several stages. First, the browser reviews the page code, then erases the element, then refreshes the DOM, followed by the copying of the parent and child CSS, updating the coordinates of the current elements on the page, and finally, redrawing the tree. In fact, in addition to updating the DOM itself, there are several other accompanying procedures, implementation of which is complex, capacitive and, thus, slows the application’s operation greatly. Each of the DOM’s updates also involves the execution of those steps. This is why the operating over the real DOM may become a real pain.

What about virtual DOM then? Virtual DOM is a lightweight copy of a real DOM, which by means of the declarative API and the diff algorithm compares those elements that need to be modified with the help of observables, and then redraws only them. And, despite the fact that virtual DOM is created from scratch every time, it takes less than 50 milliseconds, which is not noticeable to the human visual perception. This technique speeds up the performance of the application at times because it does not involve an unnecessary number of real DOM’s “heavier” elements that retain their states.

In this regard, AngularJS works somewhat differently. It employs the so-called dirty checking to discover the nodes that must be redrawn. Since dirty checking does not begin immediately but after a while, as the dynamic components of the application increase, its performance slows down.

Therefore, answering the question “why is ReactJS fast”, we mention the virtual DOM first.

? Let’s take a look at React.js and React Native features to see in which aspects their approach to development is the same, and where they differ.

Yes, React is fast. But not just thanks to the above feature. Below we will look at a few more useful tools that will make your application more efficient.

– Production Build. The traditional way of assembling ReactJS code includes the debugging and reporting routines into a ready build. Unfortunately, this happens at the expense of the application performance, which can be quite noticeable for the user. To solve this problem (which, incidentally, is inherent to many other libraries/frameworks), the ReactJS creators propose to run the build assembly using the “npm run” command. Alternatively, if you are using Webpack to create the application, you can open it directly, using the “-p” specifier (“webpack -p”). Thus, a minified and extremely responsive production build is created.

A couple more features and you will understand why the question “is ReactJS faster than many other libraries/frameworks?” can be considered rhetorical.

– Separation to Chunk Files. If you use the Webpack tool to create a ReactJS-based application, which includes many templates, breaking its code down into chunk files is instrumental to ensuring its high performance. In fact, this is done in order to establish a compromise between the number of requests (a large number of simultaneous requests even with the use of “lazy” loading entails an increased burden on the web server) and file linking (modular files require only one HTTP request to the server per file, but since they will all be executed in the queued order, this will lead to a large initial delay on the client side). In turn, plugins such as CommonsChunkPlugin and ExtractTextWebpackPlugin help to extract the code common to several files or CSS structures – to a separate file in the latter case. Such an approach to the organization of the ReactJS application architecture allows using synchronous data loading and storing those that do not need a frequent refresh to cache.

– Gzip Compression. If you simply enable the automatic compression of Javascript files on a web server, you can reduce the total amount of transmitted user requests by dozens. Depending on the webserver, you can select different modules to enable Gzip on-the-fly compression: Apache, Nginx.

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Why is ReactJS Fast? Summary So, is React JS fast? As you can see, in addition to the virtual DOM, there are several extremely useful tools that can speed up your application. On the other hand, is it really worth choosing ReactJS for development, only because of this advantage? Definitely not. In particular, in some cases, Angular apps are more efficient than React. Nevertheless, due to the fact that the central object of our article has a smaller library size in comparison with AngularJS, it shows better performance on the client side. Therefore, before making a choice in favor of a particular tool, we recommend analyzing other criteria (ease of use, debugging, learning curve, scalability of created applications, support community, etc.) and choose the instrument suiting your needs the best.