Element: wheel event
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
wheel
event doesn't necessarily dispatch ascroll
event. For example, the element may be unscrollable at all. Zooming actions using the wheel or trackpad also firewheel
events. - A
scroll
event isn't necessarily triggered by awheel
event. Elements can also be scrolled by using the keyboard, dragging a scrollbar, or using JavaScript. - Even when the
wheel
event does trigger scrolling, thedelta*
values in thewheel
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.
The wheel
event is 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.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 thedelta*
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: #cdf;
padding: 5px;
}
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:
el.addEventListener("wheel", zoom, { passive: false });
Specifications
Specification |
---|
UI Events # event-type-wheel |
HTML Standard # handler-onwheel |
Browser compatibility
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