Write reusable UI components in JavaScript. Read and write to any data source.
Describe how you want your component to look. React will automatically compute the fastest way to keep the UI up-to-date when the data changes.
React works with the libraries and frameworks that you already know.
React components implement a `render()` method that takes input data and returns what to display. This example constructs the component using an XML-like syntax called JSX, but JSX is optional; you don't need to use it. Input data is passed to the component as XML attributes, and `render()` accesses this data via `this.props`.
In addition to taking data from its creator (accessed via `this.props`), a component can maintain internal state data (accessed via `this.state`). When a component's state data changes, the rendered markup will be updated by re-invoking `render()`. This example doesn't use JSX, but you could if you wanted to.
Using properties and state, we can put together a small Todo application. React provides an interface to the DOM via `refs`. Although event handlers appear to be rendered inline, they will be collected and implemented using event delegation.
React is flexible and provides hooks that allow you to interface with other libraries and frameworks. This example uses Showdown, an external Markdown library, to convert the textarea's value in real-time.