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November 22, 2021 13:04
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EventStreams
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<div class="container"> | |
<h1>Live RecentChange events <small>EventStreams example</small></h1> | |
<hr> | |
<span>Messages in the last second: <span id="rate-min">..</span> (average so far: <span id="rate-avg">..</span>/s)</span> | |
<pre id="feed" class="mw-feed"></pre> | |
</div> |
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(function() { | |
var eventsource = new EventSource("https://stream.wikimedia.org/v2/stream/recentchange"); | |
var feedNode = document.getElementById('feed'); | |
var rateMinNode = document.getElementById('rate-min'); | |
var rateAvgNode = document.getElementById('rate-avg'); | |
var errorNode = document.createElement('div'); | |
errorNode.className = 'alert alert-danger'; | |
var infoNode = document.createElement('div'); | |
infoNode.className = 'alert alert-info'; | |
var updateBuffer = makeDisplayBuffer(10); | |
var freq; | |
printEvent({ | |
type: 'info', | |
message: 'Connecting...' | |
}); | |
eventsource.onopen = function() { | |
printEvent({ | |
type: 'info', | |
message: 'Connected! Listening for events...' | |
}); | |
freq = new Frequency(1000, function (count, average) { | |
rateMinNode.textContent = count; | |
rateAvgNode.textContent = average; | |
}); | |
}; | |
eventsource.onmessage = function(msg) { | |
if (freq) { freq.add(1); } | |
printEvent({type: 'message', data: msg.data}); | |
}; | |
eventsource.onerror = function(msg) { | |
// Don't print {isTrusted: true}. (Is this an error?) | |
if (!msg.isTrusted) { | |
printEvent({ | |
type: 'error', | |
data: msg | |
}); | |
} | |
}; | |
function printEvent(event) { | |
var node; | |
if (event.type === 'message') { | |
var node = document.createTextNode(event.data + '\n\n'); | |
$(feedNode).prepend(node); | |
updateBuffer(node); | |
} else if (event.type === 'error') { | |
$(errorNode).empty().text('ERROR: ' + JSON.stringify(event.data)); | |
if (!errorNode.parentNode) { | |
$(feedNode).before(errorNode); | |
} | |
} else if (event.type === 'info') { | |
$(infoNode).text(event.message); | |
if (!infoNode.parentNode) { | |
$(feedNode).prepend(infoNode); | |
updateBuffer(infoNode); | |
} | |
} | |
} | |
function makeDisplayBuffer(size) { | |
var buffer = []; | |
return function (element) { | |
buffer.push(element); | |
if (buffer.length > size) { | |
var popped = buffer.shift(); | |
popped.parentNode.removeChild(popped); | |
} | |
} | |
} | |
}()); | |
function Frequency(interval, callback) { | |
var freq = this; | |
var rAF = window.requestAnimationFrame || setTimeout; | |
this.interval = interval; | |
this.callback = callback; | |
this.count = 0; | |
this.total = 0; | |
this.since = this.start = this.now(); | |
function checker() { | |
freq.check(); | |
rAF(checker); | |
} | |
rAF(checker); | |
} | |
Frequency.prototype.now = ( function () { | |
var perf = window.performance; | |
return perf.now ? | |
function () { return perf.now(); } : | |
function () { return +new Date(); }; | |
}() ); | |
Frequency.prototype.add = function (count) { | |
this.count += count; | |
this.total += count; | |
this.check(); | |
}; | |
Frequency.prototype.check = function () { | |
var count, avg, ellapsedTotal; | |
var ellapsed = this.now() - this.since; | |
if (ellapsed >= this.interval) { | |
ellapsedTotal = this.now() - this.start; | |
count = this.count; | |
// One optional digit | |
avg = (this.total / (ellapsedTotal / this.interval)).toFixed(1).replace('.0', ''); | |
this.since = this.now(); | |
this.count = 0; | |
this.callback(count, avg); | |
} | |
}; |
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<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script> |
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.mw-footer { | |
padding-top: 40px; | |
padding-bottom: 40px; | |
margin-top: 100px; | |
background: #f9f9f9; | |
color: #777; | |
text-align: center; | |
border-top: 1px solid #e5e5e5 | |
} |
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<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css" rel="stylesheet" /> |
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