Viewerframe Mode Refresh Top -

let state = mode: 'view', // 'view', 'refreshing' items: [], frameElement: document.getElementById('viewerframe'), ; async function fetchData() // Simulate API call return Array.from( length: 50 , (_, i) => Item $i + 1: Updated at $new Date().toLocaleTimeString() );

Even if the user is halfway down, clicking the button executes scrollTop = 0 after the new data is in the DOM, guaranteeing the "top" behavior. Part 5: Advanced Use Cases & Optimization The basic implementation works, but production environments require nuance. Use Case 1: Infinite Scroll + Manual Refresh Top Platforms like Twitter allow infinite scroll but also a "See new Tweets" button. That button is a classic "viewerframe mode refresh top" pattern—but with a twist: it inserts new items at the top and optionally maintains relative position. viewerframe mode refresh top

Let's build a functional "viewerframe mode refresh top" widget from scratch. We will use vanilla JavaScript for clarity. Step 1: Define the HTML Structure <div id="app"> <div class="controls"> <button id="refreshBtn">⟳ Refresh & Go to Top</button> <span id="modeIndicator">Mode: View</span> </div> <div id="viewerframe" class="viewerframe">  </div> </div> Step 2: CSS for Stable Viewerframe .viewerframe width: 100%; height: 500px; overflow-y: auto; border: 1px solid #ccc; scroll-behavior: smooth; /* For pleasant top reset */ let state = mode: 'view', // 'view', 'refreshing'

Advanced implementations use virtual scrolling (e.g., react-window or tanstack virtual ). Here, "refresh top" means resetting the virtual scroll index to 0 and discarding the cache. That button is a classic "viewerframe mode refresh

// 2. Fetch fresh data const newData = await fetchData(); state.items = newData;

render(); requestAnimationFrame(() => state.frameElement.scrollTop = 0; ); Symptoms: After refresh, there is 50px of whitespace above the first item. Cause: CSS padding or margin on the container or first child. Fix: Ensure padding-top is on the container, but the first child has no margin collapse.

const virtualizer = useVirtualizer( count: items.length, getScrollElement: () => frameRef.current, estimateSize: () => 50, ); const refreshTop = () => // Clear the cache setItems(newItems); // Scroll to the very first row virtualizer.scrollToIndex(0, align: 'start' ); ; Modern CSS introduces scroll-anchoring . Browsers try to keep the user's view stable. However, to enforce mode refresh top , you override this: