Facebook is one of the largest and most popular social media platforms in the world, with over 2.91 billion monthly active users as of the second quarter of 2022. With such a massive userbase, Facebook’s front-end needs to be able to handle incredibly high traffic and provide a seamless user experience.
For many years, Facebook used a PHP-based stack for its front-end. However, as the company and its products grew, the original front-end stack started having trouble scaling. In 2011, Facebook decided it needed to develop a new front-end stack that could handle the demands of its growing platform.
After considering their options, Facebook engineers decided to build a new JavaScript library called React. React was first used in Facebook’s News Feed in 2011 and was open sourced at JSConf US in May 2013. Since then, React has become one of the most popular front-end libraries in web development.
What is ReactJS?
ReactJS (also known simply as React) is an open-source JavaScript library used for building user interfaces. It was created in 2011 by Jordan Walke, a software engineer at Facebook.
React allows developers to build reusable UI components that manage their own state. This makes it easy to compose complex interfaces from simple building blocks. React components use a declarative programming style, where developers specify what each component should look like for different data states.
The key features of React include:
- Components – React apps are built using reusable components that manage their own state.
- Virtual DOM – React keeps a virtual DOM to optimize updates only to components that changed.
- One-way data binding – Data flows in one direction, making apps more predictable.
- JSX – React components are written using JSX, a syntax extension of JavaScript.
- Performance – React evaluates only components that need to re-render, minimizing DOM operations.
By leveraging these features, React allows developers to build complex UIs from encapsulated components that can be composed together. React promotes reusability, modularity and performance.
Why Facebook chose ReactJS
By 2011, Facebook’s web app had grown enormously complex. The original front-end stack based on PHP was having trouble scaling. The view code had become deeply intertwined with business logic, making the codebase difficult to maintain.
Facebook engineers realized they needed a front-end framework that could:
- Improve programmer productivity by promoting modular, reusable code
- Enable seamless UIs with fast, smooth updates when data changed
- Scale reliably across Facebook’s suite of products
- Support both desktop and mobile experiences
After surveying the landscape of JavaScript frameworks, Facebook determined that no existing solution met their needs. So they decided to build a new open-source JavaScript library called React.
Facebook chose to build React because it:
- Uses a declarative programming style for building UIs
- Leverages a virtual DOM for performance
- Enables seamless composition of components
- Focuses exclusively on UI rendering
- Can be layered on top of existing code
React’s component architecture and virtual DOM diffing allowed Facebook to build modular UIs that remained performant at scale. React allowed their web app to evolve from a monolithic codebase into reusable, compartmentalized components. Engineers could build new features in isolation and seamlessly compose them together.
By open-sourcing React, Facebook enabled the broader web community to benefit from the same solutions to front-end scaling challenges. React has since become one of the most popular front-end libraries used by major companies including Netflix, Airbnb, Uber and Twitter.
How Facebook uses React today
Since first using React in 2011, Facebook has continued improving and expanding its React codebase. Today, React is deeply integrated into Facebook’s front-end architecture.
Some of the key ways Facebook uses React:
- News Feed – The News Feed was React’s first major product integration.
- Posts and comments – The posts and comments UI is built with React.
- Ads – The Ad Manager UI uses React components.
- Search – React powers Facebook’s search experience.
- Timeline and profiles – The Timeline and profile pages leverage React.
- Facebook UI framework – React components power Facebook’s cross-product UI framework.
- Instagram – React is used extensively on Instagram web views.
- VR – Facebook’s Oculus Rift UI contains numerous React components.
Beyond product implementations, Facebook leverages React in many other parts of its web stack including:
- Flux – React components are often used with Facebook’s Flux architecture.
- Relay – Relay is Facebook’s GraphQL client for React.
- Jest – Jest is Facebook’s JavaScript testing framework that works well with React.
- React Native – Cross-platform mobile apps can be built with React Native.
- ReasonML – Facebook created ReasonML, a new language that compiles to React.
Facebook remains committed to investing in React’s ongoing development. As new products and platforms emerge, expect Facebook to continue leveraging React extensively in its front-end stack.
Conclusion
In summary:
- Facebook built React in 2011 to solve front-end scaling issues with its growing platform.
- React’s component model enables modular, reusable UI code.
- React can efficiently render updates via its virtual DOM diffing.
- Leading products like News Feed, Timeline, Ads, and Search all use React.
- Facebook open-sourced React so others could benefit from its front-end innovations.
- React remains deeply integrated into Facebook’s web architecture today.
React has become a transformative front-end technology not just for Facebook, but for the broader web ecosystem. The problems it solves around modular UIs and performance at scale make React well-suited for large, complex web applications. As Facebook continues to innovate, expect them to push the boundaries of what’s possible with React and transform the user experience across its family of products.