MouseEvent.movementY

The movementY read-only property of the MouseEvent interface provides the difference in the Y 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.movementY = currentEvent.screenY - previousEvent.screenY.

var yShift = instanceOfMouseEvent.movementY;

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.innerText = `movement: ${event.movementX}, ${event.movementY}\n${log.innerText}`;
}

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

• MouseEvent.movementX
• MouseEvent
• Pointer Lock