React
React.js (or simply React) is an open-source Javascript library for building user interfaces (UI). React enables the creation of module-like pieces of code called Components, which reflect a particular part of the UI and can be reused across several web pages.
In contrast to the traditional ways of manipulating the DOM through query selectors, React utilizes the virtual DOM - a localized copy of the DOM - to keep the UI and the state (of the changing data) in sync. It uses reconciliation to compare the current copy to the previous one and only update part of the DOM where there are changes.
React was originally created by Jordan Walke, a software engineer at Facebook.
Example
Although React is defined as a JavaScript library, it has several characteristics of a framework.