What is Server Sent Events ?
Server-sent events (SSE) is a technology where a browser receives automatic updates from a server via HTTP connection. The Server-Sent Events EventSource API is standardized as part of HTML5 by the W3C.
The server-sent event API is contained in the EventSource interface; to open a connection to the server to begin receiving events from it, create a new EventSource object specifying the URI of a script that generates the events.
var evtSource = new EventSource("demo.php");
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