API Reference

$.SSE(url, settings)

Creates a new Server-Sent Events instance.

Parameters

Parameter	Type	Required	Description
url	string	Yes	The URL endpoint that will send SSE events
settings	object	No	Configuration object with callbacks, options, headers, and events

Returns

Returns an SSE instance object with the following methods and properties:

Property/Method	Type	Description
start()	function	Start the SSE connection
stop()	function	Stop the SSE connection
instance	object	The underlying EventSource or Ajax instance
type	string	Connection type: 'event' (native) or 'ajax' (fallback)

Settings Object

Callbacks

onOpen(event)

Called when the connection is established for the first time.

onOpen: function(e) {
    console.log('Connection opened', e);
}

Parameters:

• event (object): The event object from EventSource or synthetic event from Ajax

onEnd(event)

Called when the connection is closed.

onEnd: function(e) {
    console.log('Connection closed', e);
}

Parameters:

• event (object): The event object

onError(event)

Called when an error occurs.

onError: function(e) {
    console.error('Connection error', e);
}

Parameters:

• event (object): The error event object

onMessage(event)

Called when a message is received without a custom event name.

onMessage: function(e) {
    console.log('Data:', e.data);
    console.log('ID:', e.lastEventId);
    console.log('Origin:', e.origin);
}

Parameters:

• event (object): The message event object
  • data (string): The message data
  • lastEventId (string): The ID of the last event
  • origin (string): The origin URL
  • returnValue (boolean): Always true

Options

Configuration options for the SSE connection.

options: {
    forceAjax: false
}

Option	Type	Default	Description
forceAjax	boolean	false	Force Ajax polling even if EventSource is supported

Headers

Custom HTTP headers to send with the request.

headers: {
    'Authorization': 'Bearer token',
    'X-Custom-Header': 'value'
}

warning

Providing custom headers automatically enables Ajax mode, as native EventSource doesn't support custom headers.

Events

Custom event handlers for named server events.

events: {
    eventName: function(e) {
        console.log('Custom event:', e.data);
    }
}

Event Handler Parameters:

• event (object): The message event object (same structure as onMessage)

Instance Methods

start()

Starts the SSE connection. Can be called after creating the instance or after calling stop().

var sse = $.SSE('sse-server.php', {
    onMessage: function(e) {
        console.log(e.data);
    }
});

sse.start();

Returns: boolean

• true: Connection started successfully
• false: Connection is already running

Behavior:

1. Checks if an instance already exists
2. Determines whether to use native EventSource or Ajax fallback based on:
   • Browser support for EventSource
   • forceAjax option
   • Presence of custom headers
3. Initializes the appropriate connection method

stop()

Stops the SSE connection and cleans up resources.

sse.stop();

Returns: boolean

• true: Connection stopped successfully
• false: No active connection to stop

Behavior:

1. Checks if an instance exists
2. Closes the connection (EventSource) or stops Ajax polling
3. Calls the onEnd callback
4. Cleans up instance and type properties

Instance Properties

instance

The underlying connection object:

• For native EventSource: The EventSource instance
• For Ajax fallback: An object containing polling state

console.log(sse.instance);

type

The connection type being used:

• 'event': Using native EventSource
• 'ajax': Using Ajax fallback
• null: No active connection

console.log(sse.type);  // 'event' or 'ajax'

Server Message Format

Basic Message

data: message content

Message with Event Name

event: customEventName
data: message content

Message with ID

id: unique-message-id
data: message content

Message with Retry

retry: 3000
data: message content

Multi-line Data

data: line 1
data: line 2
data: line 3

Complete Message Example

id: 123
event: notification
retry: 5000
data: {"user": "john", "message": "Hello"}

Internal Properties

The following properties are used internally and should not be modified:

• _url: The SSE endpoint URL
• _remoteHost: The remote host (used for Ajax mode)
• _settings: The merged settings object
• _start: Reference to the original start method

Minification

To minify the library for production:

apt install uglifyjs

uglifyjs --compress 'drop_console,drop_debugger' --mangle -r '$,require,exports,_' -o jquery.sse.min.js jquery.sse.js