react-diagrams/diagrams-demo-gallery/demos/helpers/Helper.tsx

import * as React from 'react';

export class Helper {
	/**
	 * Logs the mouse position in the console, but overlays a div that consumes all events
	 * since the actual story book stories are rendered as an iFrame.
	 */
	static logMousePosition() {
		let element = window.parent.document.createElement('mouse-position');
		element.style.position = 'absolute';
		element.style.top = '0px';
		element.style.left = '0px';
		element.style.bottom = '0px';
		element.style.right = '0px';
		element.style.zIndex = '10';
		window.parent.document.body.appendChild(element);

		window.parent.window.addEventListener('mousemove', (event) => {
			console.clear();
			console.log(event.clientX, event.clientY);
		});
	}
}