React is one of Facebook's first open source projects that is both under very active development and is also being used to ship code to everybody on [facebook.com](https://www.facebook.com). We're still working out the kinks to make contributing to this project as easy and transparent as possible, but we're not quite there yet. Hopefully this document makes the process for contributing clear and answers some questions that you may have.
In React, you can create distinct components that encapsulate behavior you need. Then, you can render only some of them, depending on the state of your application.
Form components such as `<input>`, `<textarea>`, and `<option>` differ from other native components because they can be mutated via user interactions. These components provide interfaces that make it easier to manage forms in response to user interactions.
The easiest way to get started with React is to use [this Hello World example code on CodePen](http://codepen.io/gaearon/pen/ZpvBNJ?editors=0010). You don't need to install anything; you can just open it in another tab and follow along as we go through examples. If you'd rather use a local development environment, check out the [Installation](/docs/installation.html) page.
Internally, React uses several clever techniques to minimize the number of costly DOM operations required to update the UI. For many applications, using React will lead to a fast user interface without doing much work to specifically optimize for performance. Nevertheless, there are several ways you can speed up your React application.
React implements a browser-independent DOM system for performance and cross-browser compatibility. We took the opportunity to clean up a few rough edges in browser DOM implementations.
[Components](/react/docs/components-and-props.html) let you split the UI into independent, reusable pieces, and think about each piece in isolation. `React.Component` is provided by [`React`](/react/docs/react-api.html).
`React` is the entry point to the React library. If you use React as a script tag, these top-level APIs are available on the `React` global. If you use ES6 with npm, you can write `import React from 'react'`. If you use ES5 with npm, you can write `var React = require('react')`.
React and [Web Components](https://developer.mozilla.org/en-US/docs/Web/Web_Components) are built to solve different problems. Web Components provide strong encapsulation for reusable components, while React provides a declarative library that keeps the DOM in sync with your data. The two goals are complementary. As a developer, you are free to use React in your Web Components, or to use Web Components in React, or both.
Dan Abramov
8 years ago