Full example

import * as React from 'react';

interface IState {
	clicks: number;
}

export class Clicker extends React.Component<any, IState> {
	constructor(props) {
		super(props);

		this.state = {
			clicks: 0,
		};
	}

	public clickHandler = () => {
		this.setState({ clicks: this.state.clicks + 1 });
	}

	public render() {
		return (
			<div>
				<p>You have clicked the button {this.state.clicks} time(s).</p>
				<p>
					<button onClick={this.clickHandler}>click me</button>
				</p>
			</div>
		);
	}
}