Element: wheel event
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
The wheel event fires when the user rotates a wheel button on a pointing device (typically a mouse). It is also fired for related devices that simulate wheel actions, such as trackpads and mouse balls.
This event replaces the non-standard deprecated mousewheel event.
Don't confuse the wheel event with the scroll event:
- A
wheelevent doesn't necessarily dispatch ascrollevent. For example, the element may be unscrollable at all. Zooming actions using the wheel or trackpad also firewheelevents (withctrlKeyset to true). - A
scrollevent isn't necessarily triggered by awheelevent. Elements can also be scrolled by using the keyboard, dragging a scrollbar, or using JavaScript. - Even when the
wheelevent does trigger scrolling, thedelta*values in thewheelevent 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.
The wheel event is cancelable. In some browsers, only the first wheel event in a sequence is cancelable, and later events are non-cancelable. If the event is canceled, no scrolling or zooming is performed. This may cause performance issues as the browser has to wait for every wheel event to be processed before actually scrolling the content. You can avoid this by setting passive: true when calling addEventListener(), which may cause the browser to generate non-cancelable wheel events.
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.deltaXRead only-
Returns a
doublerepresenting the horizontal scroll amount. WheelEvent.deltaYRead only-
Returns a
doublerepresenting the vertical scroll amount. WheelEvent.deltaZRead only-
Returns a
doublerepresenting the scroll amount for the z-axis. WheelEvent.deltaModeRead only-
Returns an
unsigned longrepresenting the unit of thedelta*values' scroll amount. Permitted values are:Constant Value Description WheelEvent.DOM_DELTA_PIXEL0x00The delta*values are specified in pixels.WheelEvent.DOM_DELTA_LINE0x01The 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_PAGE0x02The delta*values are specified in pages. Each mouse click scrolls a page of content. WheelEvent.wheelDeltaRead only Deprecated-
Returns an integer (32-bit) representing the distance in pixels.
WheelEvent.wheelDeltaXRead only Deprecated-
Returns an integer representing the horizontal scroll amount.
WheelEvent.wheelDeltaYRead 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
| Specification |
|---|
| UI Events # event-type-wheel |
| HTML # handler-onwheel |
Browser compatibility
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