Onslide

Onslide is a term used in web UI development to describe a callback or event fired when a slide transition occurs in a slideshow or carousel. It is not part of the standard DOM specification; its exact form and payload depend on the library or framework implementing the component. The callback is typically used to react to the active slide changing, such as updating indicators, loading content for the next slide, or sending analytics data.

Implementation and naming of onslide vary by library. Some libraries expose an onslide option or property in their carousel component that you assign to a function. Others emit a slide-related event to which you attach a listener, with the event name differing by library (for example, a generic slide event or a library-specific name). In frameworks that use template bindings, onslide may be wired through a directive or binding mechanism.

In practice, examples of usage differ across ecosystems. Bootstrap’s carousel, for instance, fires slide-related events during sliding and can be wired to via a listener named for the library’s event system. React and Vue wrappers may expose onSlide as a callback prop or use a similar binding to respond to slide changes. The exact syntax and event names depend on the chosen library or framework, so consulting the respective documentation is essential.

Considerations when using onslide include understanding that it is not standardized, so code portability is limited. Typical payloads may include the indices of the previous and next slides and the direction of movement. Accessibility and performance should be considered, ensuring transitions can be paused or controlled and that keyboard navigation remains functional.

See also: Carousel, Slideshow, Event handling, onChange.