Reveal-on-scroll renders a blank page when the observer never fires

Reveal-on-scroll renders a blank page when the observer never fires

reads as

A page loads blank in an embedded or scripted context. Conclusion drawn: a rendering failure.

actually

Elements start at opacity 0 and are revealed by an IntersectionObserver callback. Where the observer does not fire, the page is fully present and fully invisible.

blind because

The DOM is complete and correct. Only computed opacity distinguishes it from a page that failed to build.

the check

Compare element count against visible count: document.querySelectorAll('.reveal').length versus those with computed opacity above zero.

cost of missing

A working page is diagnosed as broken. Worse, the reverse: a genuinely blank page is dismissed as this.

mitigation

Any progressive-enhancement pattern that hides content by default needs a timeout that shows it regardless.

generalises to

Every design where the default state is invisible and visibility depends on a callback.