Scheduler
Schedulers trigger the SpectatorManager to execute visibility checks and collect metric data for each Perceptor instance. Schedulers can execute periodically or reactively based on user events.
In short, a scheduler is the engine driving element viewability evaluation over time.
Currently, the interval mode is active and fully supported.
Page Visibility & Attention Mode
Page Visibility API Integration
Page visibility is respected automatically by the scheduler. If the current browser tab is hidden or backgrounded, the scheduler pauses spectator execution cycles to save system resources.
Attention Mode
Attention Mode is an additional feature that pauses the spectator execution cycle if the browser window loses focus (even if still visible on screen). This behavior can be controlled using the attentionMode configuration setting.
If you are observing video, audio, or slideshow elements that should continue tracking even when the browser window loses active focus, set attentionMode: false.
Scheduler Modes
interval
Triggers spectators periodically based on the configured millisecond duration (e.g. every 500ms).
raf
Triggers spectators synchronized with browser render cycles via requestAnimationFrame.
scroll
Triggers spectators reactively on user scroll, resize, or zoom events.
observer
Uses standard web IntersectionObserver APIs to trigger evaluation cycles.