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.

You can set the onmessage attribute to a JavaScript function to receive non-typed messages (that is, messages with no event field). You can also call addEventListener() to listen for events just like any other event source.

See Using server-sent events for further details.

Method overview

Properties

In addition to these exposed attributes, there are two internal attributes that are not exposed directly:

reconnection time

This is a time, in milliseconds, used to determine how long to wait after a failed attempt to connect before trying again.

last event ID string

This is initially the empty string; the server can send a message with the field name id to set this value.

Constants

Methods

close()

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

void close();

Parameters

None.

Initializes the object for use from C++ code with the principal, script context, and owner window that should be used.

void init(
  in nsIPrincipal principal,
  in nsIScriptContext scriptContext,
  in nsPIDOMWindow ownerWindow,
  in DOMString url
);

Parameters

principal

The principal to use for the request. This must not be null.

scriptContext

The script context to use for the request. May be null.

ownerWindow

The associated window for the request. May be null.

url

The EventSource's URL. This must not be empty.

See also

• Server-Sent Events: The EventSource InterfaceCR
• Using server-sent events

Browser compatibility