gistfile1.txt

function EventSource (url)
{
	this.url = url;
	this.offset = 0;
	this.prefix = "data: ";
	this._resetWorkaround();
}

EventSource.prototype._resetWorkaround = function () {
	if (this.ajax) {
		this.ajax.onreadystatechange = null;
		this.ajax.abort();
	}
	this.offset = 0;
	this.ajax = new XMLHttpRequest();
	this.ajax.onreadystatechange = this._onchange.bind(this);
	this.ajax.open("GET", this.url);
	this.ajax.send();
}

EventSource.prototype._onchange = function () {
	let msg = this.ajax.responseText.slice(this.offset);
	this.offset += msg.length;
	if (msg.startsWith(this.prefix)) {
		let data = msg.replace(this.prefix, "");
		this.onmessage({ data:data });
	}
	// we get high cpu and mem usage if we dont reset this...
	if (this.offset >= 10000000) {
		this._resetWorkaround();
	}
}

EventSource.prototype.onmessage = function (msg) {
	console.log("message", msg.data);
}