Selective hydration

<section class="stage"><div class="heading">SELECTIVE HYDRATION <span class="hint">interaction first</span></div><div class="hydration-lanes"><div class="lane" data-lane="feed"><b>FEED</b><span class="meter"><i></i></span><em>waiting</em></div><div class="lane" data-lane="comments"><b>COMMENTS</b><span class="meter"><i></i></span><em>waiting</em></div><div class="lane" data-lane="search"><b>SEARCH</b><span class="meter"><i></i></span><em>waiting</em></div></div><div class="caption" id="hydrate-note">Tap comments: its boundary takes priority</div></section>

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const lanes=[...document.querySelectorAll(".lane")],note=document.getElementById("hydrate-note");let step=0;function tick(){const active=step===0?[]:step===1?[1]:[1,0,2];lanes.forEach((lane,i)=>{lane.classList.toggle("active",active.includes(i));lane.querySelector("em").textContent=active.includes(i)?"ready":"waiting"});note.textContent=step===0?"Tap comments: its boundary takes priority":step===1?"Comments respond before other regions":"Remaining regions hydrate afterwards";step=(step+1)%3}tick();const timer=setInterval(tick,1050);lanes.forEach((lane,i)=>lane.addEventListener("pointerdown",()=>{clearInterval(timer);step=i===1?1:2;tick()}))