WheelEvent: deltaZ property

The WheelEvent.deltaZ read-only property is a double representing the scroll amount along the z-axis, in the WheelEvent.deltaMode unit.

You must check the deltaMode property to determine the unit of the deltaZ value. Do not assume that the deltaZ value is specified in pixels. Some browsers, for compatibility reasons, may return different units for the deltaZ value depending on whether deltaMode has been accessed, to accommodate for websites not explicitly checking the deltaMode property.

const syntheticEvent = new WheelEvent("syntheticWheel", {
  deltaZ: 4,
  deltaMode: 0,
});

console.log(syntheticEvent.deltaZ);