Element: wheel event

The wheel event fires when the user rotates a wheel button on a pointing device (typically a mouse).

This event replaces the non-standard deprecated mousewheel event.

Note: Don't confuse the wheel event with the scroll event. The default action of a wheel event is implementation-specific, and doesn't necessarily dispatch a scroll event. Even when it does, the delta* values in the wheel event don't necessarily reflect the content's scrolling direction. Therefore, do not rely on the wheel event's delta* properties to get the scrolling direction. Instead, detect value changes of scrollLeft and scrollTop of the target in the scroll event.

Syntax

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

js

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

onwheel = (event) => {};

Event type

A WheelEvent. Inherits from Event.

Event UIEvent MouseEvent WheelEvent

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

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

WheelEvent.wheelDeltaX Read only

Returns an integer representing the horizontal scroll amount.

WheelEvent.wheelDeltaY Read only

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.

html

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

css

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

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

js

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})`;
}

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

addEventListener equivalent

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

js

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

Specifications

Specification
UI Events
# event-type-wheel
HTML Standard
# handler-onwheel

Browser compatibility

BCD tables only load in the browser

See also