WheelEvent.deltaMode

The WheelEvent.deltaMode read-only property returns an unsigned long representing the unit of the delta values scroll amount. Permitted values are:

Constant	Value	Description
DOM_DELTA_PIXEL	0x00	The delta values are specified in pixels.
DOM_DELTA_LINE	0x01	The delta values are specified in lines.
DOM_DELTA_PAGE	0x02	The delta values are specified in pages.

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

console.log(syntheticEvent.deltaMode);