Nullable PropType for React

prop_nullable.js

/**
 * Usage:
 * 
 * import React from 'react';
 * import nullable from 'prop_nullable';
 * 
 * let myClass = React.createClass({
 *    propTypes: {
 *      myProp: nullable( React.PropTypes.string ).isRequired,
 *      myOtherProp: nullable( [React.PropTypes.string, React.PropTypes.number] )
 *    }
 * });
 */
import { PropTypes } from 'react';

let { oneOf, oneOfType } = PropTypes;

export default types => oneOfType( [ oneOf( [ null ] ), ...[].concat( types ) ] );

Nice, I hope something like this is integrated in React. Although I like the Joi way for validations more.
https://github.com/hapijs/joi

You can do something like this:

Joi.string().allow(null).required();

A "white list" like allow(whatever) is more flexible.

This doesn't raise any warning if types is undefined.