Callback parameters (event)

The callback function automatically receives a parameter with some information on the source event. 
document.addEventListener('click', actionClick );

function actionClick(event) {

  const button = event.button;
  const x = event.clientX;
  const y = event.clientY;

  const newElement = document.createElement('p');
  newElement.textContent = `Click ${button} at position (${x},${y})`;
  document.querySelector("body").appendChild(newElement);
}