React is an open source JavaScript library and a convenient tool for creating user interfaces. Its main task is to provide a display of what can be seen on web pages.
React makes it easy to create interfaces by splitting each page into small sections, i.e. it uses the so-called component approach.
There are no controllers, views, patterns, etc. The components can be reused, borrowed from each other, and linked. This serves as a kind of building unit from which the interface is assembled.
In other words, the React component is a piece of code that represents an element of a web page.
The developer creates small parts of the code that can be combined to form larger ones or to use them as independent interface elements.
The most important thing in this concept is that both large and small components can be reused in the new projects.
To form a page, developers call these functions in a specific order, collect the results together, and show them to the user.
React was created by Jordan Walker, a software developer at Facebook. It was influenced by the XHP - component HTML framework for PHP. The first time React was used in Facebook news feed in 2011 and later on Instagram in 2012. React source code was unveiled in May 2013 at the JSConf US conference.
React Native was announced at the Facebook conference “React.js Conf” in February 2015, and the source code was opened in March 2015. It allows programmers to develop native iOS, Android, and UWP apps.
On April 18, 2017, Facebook announced React Fiber, a rewritten and optimized version of this JS library. React Fiber replaced the old version of React and all modern features and enhancements are implemented on a new syntax, React Fiber.