MouseEvent.movementX

The movementX read-only property of the MouseEvent interface provides the difference in the X coordinate of the mouse pointer between the given event and the previous mousemove event. In other words, the value of the property is computed like this: currentEvent.movementX = currentEvent.screenX - previousEvent.screenX.

var xShift = instanceOfMouseEvent.movementX;

A number

This example logs the amount of mouse movement using movementX and movementY.

<p id="log">Move your mouse around.</p>

function logMovement(event) {
  log.insertAdjacentHTML('afterbegin', `movement: ${event.movementX}, ${event.movementY}<br>`);
  while (log.childNodes.length > 128) log.lastChild.remove()
}

const log = document.getElementById('log');
document.addEventListener('mousemove', logMovement);

• MouseEvent.movementY
• MouseEvent
• Pointer Lock