React.createClass({  propTypes: {    // You can declare that a prop is a specific JS primitive. By default, these    // are all optional.    optionalArray: React.PropTypes.array,    optionalBool: React.PropTypes.bool,    optionalFunc: React.PropTypes.func,    optionalNumber: React.PropTypes.number,    optionalObject: React.PropTypes.object,    optionalString: React.PropTypes.string,    optionalSymbol: React.PropTypes.symbol,    // Anything that can be rendered: numbers, strings, elements or an array    // (or fragment) containing these types.    optionalNode: React.PropTypes.node,    // A React element.    optionalElement: React.PropTypes.element,    // You can also declare that a prop is an instance of a class. This uses    // JS's instanceof operator.    optionalMessage: React.PropTypes.instanceOf(Message),    // You can ensure that your prop is limited to specific values by treating    // it as an enum.    optionalEnum: React.PropTypes.oneOf(['News', 'Photos']),    // An object that could be one of many types    optionalUnion: React.PropTypes.oneOfType([      React.PropTypes.string,      React.PropTypes.number,      React.PropTypes.instanceOf(Message)    ]),    // An array of a certain type    optionalArrayOf: React.PropTypes.arrayOf(React.PropTypes.number),    // An object with property values of a certain type    optionalObjectOf: React.PropTypes.objectOf(React.PropTypes.number),    // An object taking on a particular shape    optionalObjectWithShape: React.PropTypes.shape({      color: React.PropTypes.string,      fontSize: React.PropTypes.number    }),    // You can chain any of the above with `isRequired` to make sure a warning    // is shown if the prop isn't provided.    requiredFunc: React.PropTypes.func.isRequired,    // A value of any data type    requiredAny: React.PropTypes.any.isRequired,    // You can also specify a custom validator. It should return an Error    // object if the validation fails. Don't `console.warn` or throw, as this    // won't work inside `oneOfType`.    customProp: function(props, propName, componentName) {      if (!/matchme/.test(props[propName])) {        return new Error(          'Invalid prop `' + propName + '` supplied to' +          ' `' + componentName + '`. Validation failed.'        );      }    },    // You can also supply a custom validator to `arrayOf` and `objectOf`.    // It should return an Error object if the validation fails. The validator    // will be called for each key in the array or object. The first two    // arguments of the validator are the array or object itself, and the    // current item's key.    customArrayProp: React.PropTypes.arrayOf(function(propValue, key, componentName, location, propFullName) {      if (!/matchme/.test(propValue[key])) {        return new Error(          'Invalid prop `' + propFullName + '` supplied to' +          ' `' + componentName + '`. Validation failed.'        );      }    })  },  /* ... */});