MyComponent.tsx

import * as React from "react";

interface MyComponentProps {
  name: string;
  countryCode?: string;
}

class MyComponent extends React.Component<MyComponentProps, {}> {
  render() {
    const { name, countryCode } = this.props;

    return (
      <div>
        User: { name } <br/>
        Country: { countryCode.toUpperCase() } // nope
      </div>
    );
  }
}