How to declare defaultProps on a React component class using TypeScript?

You can define default props this way:

export class Counter extends React.Component {
  constructor(props) {
    super(props);
    this.state = {count: props.initialCount};
    this.tick = this.tick.bind(this);
  }
  tick() {
    this.setState({count: this.state.count + 1});
  }
  render() {
    return (
      <div onClick={this.tick}>
        Clicks: {this.state.count}
      </div>
    );
  }
}
Counter.propTypes = { initialCount: React.PropTypes.number };
Counter.defaultProps = { initialCount: 0 };

This is equivalent in TypeScript to defining defaultProps as a static field inside the class body:

class SomeComponent extends Component<IProps, IStates> {
    public static defaultProps: IProps = { /* ... */ }; 
    // ...
}