How a One-Line State Bug Caused Infinite Scroll to Replace Posts Instead of Appending

A developer building infinite scroll in the ICanUp app discovered that newly loaded pages were replacing existing posts rather than appending to them. The root cause was a single assignment statement that overwrote the posts array on every page load, regardless of whether it was an initial fetch or a continuation. The fix required conditional state logic: page 1 sets the list fresh, while subsequent pages spread new results onto the existing array. Additional safeguards — including pagination metadata, duplicate deduplication via Map, and a loading guard — were needed to prevent repeated requests and post-final-page fetches. The case highlights that infinite scroll and traditional pagination share the same data-fetching mechanics but require fundamentally different rules for updating local state.