proptypes

MyComponent.propTypes = {
  items: PropTypes.arrayOf(
    PropTypes.shape({
      code: PropTypes.string,
      id: PropTypes.number,
    })
  ),
};

import PropTypes from 'prop-types';

class Greeting extends React.Component {
  render() {
    return (
      <h1>Hello, {this.props.name}</h1>
    );
  }
}

Greeting.propTypes = {
  name: PropTypes.string
};

npm install --save prop-types

size: PropTypes.oneOfType([
  PropTypes.string,
  PropTypes.number
]),

import PropTypes from 'prop-types'; // ES6
var PropTypes = require('prop-types'); // ES5 with npm