Glossary coding Term Page
IntersectionObserver
Observe when a target crosses visibility thresholds to trigger work just in time.
Core Idea
IntersectionObserver lets you declaratively watch targets and receive batched entries whenever they intersect the viewport or a custom root. You can tune thresholds to fire once, toggle classes, or start loading content precisely when users approach it.
Why It Matters Here
Mathbong leans on observers to power lazy loading demos without scroll listeners or manual math. They keep render helpers tidy and pave the way for performance instrumentation later in the series.