React
Noun · Development · Origin: 2013
Definitions
React is a JavaScript library for building user interfaces, created by Facebook (now Meta) and open-sourced in 2013. It introduced a component-based architecture where the UI is broken into reusable, self-contained pieces that manage their own state. React uses a virtual DOM, an in-memory representation of the real DOM, to efficiently determine the minimum number of updates needed when data changes, resulting in fast rendering performance. Developers write components using JSX, a syntax extension that lets you write HTML-like markup directly in JavaScript. React supports both class components and, since the introduction of Hooks in version 16.8, function components with state and lifecycle capabilities. The ecosystem includes React Router for navigation, Redux and Zustand for state management, and Next.js for server-side rendering and static site generation. React is one of the most widely adopted frontend technologies, used by companies like Meta, Netflix, Airbnb, and Uber to build complex, interactive web applications.
In plain English: The most popular tool for building interactive websites, created by Facebook — lets developers build UIs from reusable building blocks called components.
Origin Story
The JavaScript library born from a Facebook ads bug
**React** was created by **Jordan Walke** at Facebook in 2011. The catalyst was a frustrating bug in Facebook's ads application: the notification count for chat messages, friend requests, and other updates kept falling out of sync. The underlying problem was that the app's UI state was being managed imperatively — manually updating DOM elements when data changed — and the cascading updates were nearly impossible to keep consistent.
Walke's radical idea was to re-render the entire UI from scratch whenever state changed, using a **virtual DOM** to efficiently diff the desired output against the actual DOM and apply only the minimum necessary changes. This declarative approach meant developers described *what* the UI should look like, not *how* to update it. React was first deployed on Facebook's News Feed in 2011 and Instagram in 2012.
When React was open-sourced at JSConf US in May 2013, the reception was initially skeptical. Mixing HTML-like syntax (JSX) directly in JavaScript violated the prevailing orthodoxy of separation of concerns. But developers who tried it found that co-locating markup with logic actually made components easier to understand, and React's adoption became exponential.
Coined by: Jordan Walke (Facebook)
Context: Facebook, 2011; open-sourced May 2013
Fun fact: Jordan Walke's initial prototype was influenced by XHP, a PHP extension used at Facebook, and by functional programming concepts. He originally called the project 'FaxJS' before it was renamed to React.