JavaScript MouseEvent movementX Property

const log = document.getElementById("log");

document.addEventListener("mousemove", (event) => {
  log.textContent =
    `movement: ${event.movementX}, ${event.movementY}`;
});

document.addEventListener("click", (e) => {
  console.log({
    type: e.type,
    movementX: e.movementX, // 0
    clientX: e.clientX      // absolute position still set
  });
});

let prev = null;

document.addEventListener("mousemove", (e) => {
  const diyDx = prev == null ? 0 : e.screenX - prev;
  prev = e.screenX;

  console.log({
    movementX: e.movementX,
    diyDx
  });
});