import * as React from 'react';
import * as ReactDOM from 'react-dom';

interface ICounter{
    counter: number
}

class Button extends React.Component<any, ICounter>{
    public state = {counter: 0}

    public handleClick = () => {
        this.setState((prevState) => ({
            counter: prevState.counter + 1
        }));
    }

    public render() {
        return(
            <button onClick={this.handleClick}>
                {this.state.counter}
            </button>
        );
    }
}

export default Button;

ReactDOM.render(
    <Button />,
    document.getElementById('counter') as HTMLElement
  );