Yaj SSE

A lightweigth (<2kb) Yaj Plugin for Server-Sent Events (SSE) EventSource Polyfill. This plugin try to use the native EventSource object if it supported by the browser. If there is no native support the request is made by ajax requests (polling). You do not need to change the server side nor the client side.

Example

Client Side

var sse = new SSE('http://example.com/sse-server.php', {
    onMessage: function(e){ 
        console.log("Message"); console.log(e); 
    }
});
sse.start();

Server Side

echo "data: My Message\n";
echo "\n";

Dependencies

• Yaj (only for ajax fallback)

Install

Just download the repository and point to the Yaj plugin:

<script src="yaj-sse.js" ></script>

or

<script src="yaj-sse.min.js" ></script>

You can also install using yarn:

yarn add yaj-sse

Usage:

Constructor

var sse = new SSE(url, settings);

• url: URL for the server will be sent the events to this page;
• settings: The events and options for the SSE instance

Settings List

All the options:

var sseObject = new SSE('sse-server.php', {
    onOpen: function (e) {},
    onEnd: function (e) {},
    onError: function (e) {},
    onMessage: function (e) {},
    options: {},
    headers: {},
    events: {}
});

Event onOpen

Fired when the connection is opened the first time;

onOpen: function(e){ 
    console.log("Open"); console.log(e); 
},

Event onEnd

Fired when the connection is closed and the client will not listen for the server events;

onEnd: function(e){ 
    console.log("End"); console.log(e); 
},

Event onError

Fired when the connection error occurs;

onError: function(e){ 
    console.log("Could not connect"); 
},

Event onMessage

Fired when the a message without event is received

onMessage: function(e){ 
    console.log("Message"); console.log(e); 
},

Custom Options

Define the options for the SSE instance

options: {
    forceAjax: false
},

• forceAjax: Uses ajax even if the EventSource object is supported natively;

Custom Events

Fired when the server set the event and match with the key

For example, if you have a custom event called myEvent you may use the follow code:

events: {
    myEvent: function(e) {
        console.log('Custom Event');
        console.log(e);
    }
}

Server side:

echo "event: myEvent\n";   // Must match with events in the HTML.
echo "data: My Message\n";
echo "\n";

Custom Headers

You can send custom headers to the request.

headers: {
    'Authorization', 'Bearer 1a234fd4983d'
}

Note: As the EventSource does not support send custom headers to the request, the object will fallback automatically to 'forceAjax=true', even this it is not set.

Methods

start

Start the EventSource communication

sse.start();

stop

Stop the EventSource communication

sse.stop();

Quirks

The ajax does not support the streaming as the event source supports. In that case we recommend create a server without streaming and set the "retry" to determine query frequency;

Example Server Side:

echo "retry: 3000\n";
echo "data: My Message\n";
echo "\n";

Minify

npm run minify

Running the examples

Start the webserver:

docker run -it --rm -p 8080:80 -v $PWD:/var/www/html byjg/php:7.4-fpm-nginx 

Open the browser: http://localhost:8080/examples/sse-client.html

References

• http://www.w3.org/TR/2009/WD-eventsource-20091029/
• https://developer.mozilla.org/en-US/docs/Server-sent_events/Using_server-sent_events
• http://html5doctor.com/server-sent-events/
• http://www.html5rocks.com/en/tutorials/eventsource/basics/

---

Open source ByJG