Typescript complains Property does not exist on type ‘JSX.IntrinsicElements’ when using React.createClass?

Your component must start with a capital letter I instead of small letter i otherwise TypeScript would yell. Changing item to Item should fix it:

var Item = React.createClass({
  render: function() {
    return (<div>hello world</div>)
  }
});

export default class ItemList extends Component<any, any> {
    render() {
        return (<Item />)
    }
}