Server-Sent Events

<div class="n-demo"><div class="n-head"><strong>ONE-WAY EVENT STREAM</strong><span>LIVE TRACE</span></div><div class="n-stage"><div class="sse"><div class="sse-server n-box">SERVER</div><div class="sse-wire">→<small id="sse-wire">OPEN</small></div><div class="sse-log n-box"><span id="sse0">id: 41 · ready</span><span id="sse1">id: 42 · update</span><span id="sse2">id: 43 · done</span></div></div></div><div class="n-foot">tap to step · auto replay</div></div>

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let step=0;function advance(){for(let i=0;i<3;i++)document.getElementById('sse'+i).classList.toggle('n-on',i<=Math.min(step,2));document.getElementById('sse-wire').textContent=step===3?'RECONNECT':'OPEN';step=(step+1)%4}
const clickTarget=document.querySelector('.n-demo');if(clickTarget&&typeof advance==='function'){advance();const timer=setInterval(advance,1050);clickTarget.addEventListener('pointerdown',()=>{clearInterval(timer);advance()})}