EventSource

The EventSource interface is used to receive server-sent events. It connects to a server over HTTP and receives events in text/event-stream format without closing the connection.

Constructor

EventSource()

Creates a new EventSource from the given USVString.

Properties

This interface also inherits properties from its parent, EventTarget.

EventSource.readyState Read only

A number representing the state of the connection. Possible values are CONNECTING (0), OPEN (1), or CLOSED (2).

EventSource.url Read only

A DOMString representing the URL of the source.

EventSource.withCredentials Read only

A Boolean indicating whether the EventSource object was instantiated with CORS credentials set (true), or not (false, the default).

Event handlers

EventSource.onerror

Is an EventHandler called when an error occurs and the error event is dispatched on an EventSource object.

EventSource.onmessage

Is an EventHandler called when a message event is received, that is when a message is coming from the source.

EventSource.onopen

Is an EventHandler called when an open event is received, that is when the connection was just opened.

Methods

This interface also inherits methods from its parent, EventTarget.

EventSource.close()

Closes the connection, if any, and sets the readyState attribute to CLOSED. If the connection is already closed, the method does nothing.

Examples

var evtSource = new EventSource('sse.php');
var eventList = document.querySelector('ul');

evtSource.onmessage = function(e) {
  var newElement = document.createElement("li");

  newElement.textContent = "message: " + e.data;
  eventList.appendChild(newElement);
}

Specifications

Browser compatibility

[1] But not service workers as yet.

See also

• Using server-sent events