Server sent events (SSE): Overview

gistfile1.js

var serverEvent = new EventSource("http://example.com/eventsource.php"); //CORS is supported

serverEvent.onerror = function(event) {
  console.log(event.target.errorCode);
};

serverEvent.onopen = function() {
  console.log("Connection has been established");
};

serverEvent.onmessage = function(event) {
  console.log("Message: " + event.data); //Data can be in JSON format. Use JSON.parse if so
};

serverEvent.onnewconnection = function(event) { //User defined event
  console.log("A new user has entered the chatroom.");
};