React Scroll Effects Without External Libraries

React Scroll Effects Without External Libraries Scroll is the most fundamental user interaction on the web. Progress bars that fill as you read, headers that shrink and stick, modals that lock the page behind them, "scroll to section" buttons -- these effects appear on nearly every modern site. Yet implementing them correctly in React means juggling addEventListener, IntersectionObserver, overflow styles, and a surprising number of edge cases. Most developers either pull in a heavy animation lib