React
React uses a declarative paradigm that makes it easier to reason about
your application.
React computes the minimal set of changes necessary to keep your DOM
up-to-date.
React works with the libraries and frameworks that you already know.
Declarative
Efficient
Flexible
A Simple Component
React components implement a render() method that takes input data and
returns what to display. This example uses an XML-like syntax called
JSX. Input data that is passed into the component can be accessed by
render() via this.props.
JSX is optional and not required to use React.
A Stateful Component
In addition to taking input data (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 demonstrates use of React without JSX.
An Application
Using props and state, we can put together a small Todo application.
This example uses state to track the current list of items as well as
the text that the user has entered. Although event handlers appear to be
rendered inline, they will be collected and implemented using event
delegation.
A Component Using External Plugins
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.