let { BaseComponent, DefaultButton, TooltipHost, Fabric } = window.Fabric;

class TooltipBasicExample extends BaseComponent<any, any> {
  public render(): JSX.Element {
    return (
      <div>
        <TooltipHost content="This is the tooltip" id="myID" calloutProps={{ gapSpace: 0 }}>
          <DefaultButton aria-describedby="myID">Hover Over Me</DefaultButton>
        </TooltipHost>
      </div>
    );
  }
}

ReactDOM.render(<TooltipBasicExample />, document.getElementById('content'));