Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("wheel", (event) => { })

onwheel = (event) => { }

Event type

A WheelEvent. Inherits from MouseEvent, UIEvent and Event.

Event properties

This interface inherits properties from its ancestors, MouseEvent, UIEvent, and Event.

WheelEvent.deltaX Read only

Returns a double representing the horizontal scroll amount.

WheelEvent.deltaY Read only

Returns a double representing the vertical scroll amount.

WheelEvent.deltaZ Read only

Returns a double representing the scroll amount for the z-axis.

WheelEvent.deltaMode Read only

Returns an unsigned long representing the unit of the delta* values' scroll amount. Permitted values are:

Constant	Value	Description
WheelEvent.DOM_DELTA_PIXEL	0x00	The delta* values are specified in pixels.
WheelEvent.DOM_DELTA_LINE	0x01	The delta* values are specified in lines. Each mouse click scrolls a line of content, where the method used to calculate line height is browser dependent.
WheelEvent.DOM_DELTA_PAGE	0x02	The delta* values are specified in pages. Each mouse click scrolls a page of content.

WheelEvent.wheelDelta Read only Deprecated

Returns an integer (32-bit) representing the distance in pixels.

WheelEvent.wheelDeltaX Read only Deprecated

Returns an integer representing the horizontal scroll amount.

WheelEvent.wheelDeltaY Read only Deprecated

Returns an integer representing the vertical scroll amount.

Examples

Scaling an element via the wheel

This example shows how to scale an element using the mouse (or other pointing device) wheel.

<div>Scale me with your mouse wheel.</div>

body {
  min-height: 100vh;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

div {
  width: 105px;
  height: 105px;
  background: #ccddff;
  padding: 5px;
}

let scale = 1;
const el = document.querySelector("div");

function zoom(event) {
  event.preventDefault();

  scale += event.deltaY * -0.01;

  // Restrict scale
  scale = Math.min(Math.max(0.125, scale), 4);

  // Apply scale transform
  el.style.transform = `scale(${scale})`;
}

el.onwheel = zoom;

addEventListener equivalent

The event handler can also be set up using the addEventListener() method:

el.addEventListener("wheel", zoom, { passive: false });

Specifications

Browser compatibility

See also

• WheelEvent