SnapEvent

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The SnapEvent interface defines the event object for the scrollsnapchanging and scrollsnapchange events. Respectively, these fire on on a scroll container when the browser determines that a new scroll snap target is pending (will be selected when the current scroll gesture ends), and when a new snap target is selected.

These events can be used to run code in response to new elements being snapped to; SnapEvent exposes references to the element snapped to in the inline and/or block direction. The property values available on SnapEvent correspond directly to the value of the scroll-snap-type CSS property set on the scroll container:

If the snap axis is specified as block (or a physical axis value that equates to block in the current writing mode), only snapTargetBlock returns an element reference.
If the snap axis is specified as inline (or a physical axis value that equates to inline in the current writing mode), only snapTargetInline returns an element reference.
If the snap axis is specified as both, snapTargetBlock and snapTargetInline return an element reference.

Constructor

SnapEvent() Experimental: Creates a new SnapEvent object instance.

Instance properties

Inherits properties from its parent, Event.

snapTargetBlock Read only Experimental: Returns a reference to the element snapped to in the block direction when the event fired, or null if scroll snapping only occurs in the inline direction so no element is snapped to in the block direction.
snapTargetInline Read only Experimental: Returns a reference to the element snapped to in the inline direction when the event fired, or null if scroll snapping only occurs in the block direction so no element is snapped to in the inline direction.

Examples

`scrollsnapchanging` example

In the following scrollsnapchanging handler function snippet, we set the snapTargetBlock element's class attribute to pending using the Element.className property, which could be used to style the element differently when it becomes a pending snap target.

Note that this handler is intended to be set on a block-direction scroll container (vertically-scrolling if the page is set to a horizontal writing-mode), therefore only the snapTargetBlock element will change between multiple events firing. SnapEvent.snapTargetInline will return null, because no snapping occurs in the inline direction.

scrollingElem.addEventListener("scrollsnapchanging", (event) => {
  // Set current pending snap target class to "pending"
  event.snapTargetBlock.className = "pending";

  // Logs the new pending block-direction snap target element
  console.log(event.snapTargetBlock);

  // Logs null; no inline snapping occurs
  console.log(event.snapTargetInline);
});

`scrollsnapchange` example

In the following scrollsnapchange handler function snippet, we set a selected class on the SnapEvent.snapTargetBlock element, which could be used to style a newly-selected snap target to look like it has been selected (for example, with an animation).

scrollingElem.addEventListener("scrollsnapchange", (event) => {
  event.snapTargetBlock.className = "selected";
});

Specifications

Specification
CSS Scroll Snap Module Level 2 # snapevent-interface

Browser compatibility

BCD tables only load in the browser