This library is a pure JavaScript implementation of the EventSource client. The API aims to be W3C compatible.
You can use it with Node.js or as a browser polyfill for
browsers that don't have native EventSource
support.
- Fixes several multiple reconnect issues (these are quite serious)
- Adds a
timeout
option to manually reconnect after a specified time - Allows disabling the reconnection
npm install @joeybaker/eventsource
npm install
node ./example/sse-server.js
node ./example/sse-client.js # Node.js client
open http://localhost:8080 # Browser client - both native and polyfill
curl http://localhost:8080/sse # Enjoy the simplicity of SSE)
Just add example/eventsource-polyfill.js
file to your web page:
<script src=/eventsource-polyfill.js></script>
Now you will have two global constructors:
window.EventSourcePolyfill
window.EventSource // Unchanged if browser has defined it. Otherwise, same as window.EventSourcePolyfill
If you're using webpack or browserify
you can of course build your own. (The example/eventsource-polyfill.js
is built with webpack).
You can define custom HTTP headers for the initial HTTP request. This can be useful for e.g. sending cookies
or to specify an initial Last-Event-ID
value.
HTTP headers are defined by assigning a headers
attribute to the optional eventSourceInitDict
argument:
var eventSourceInitDict = {headers: {'Cookie': 'test=test'}};
var es = new EventSource(url, eventSourceInitDict);
By default, https requests that cannot be authorized will cause connection to fail and an exception to be emitted. You can override this behaviour:
var eventSourceInitDict = {rejectUnauthorized: false};
var es = new EventSource(url, eventSourceInitDict);
Note that for Node.js < v0.10.x this option has no effect - unauthorized HTTPS requests are always allowed.
Unauthorized and redirect error status codes (for example 401, 403, 301, 307) are available in the status
property in the error event.
es.onerror = function (err) {
if (err) {
if (err.status === 401 || err.status === 403) {
console.log('not authorized');
}
}
};
You can define a proxy
option for the HTTP request to be used. This is typically useful if you are behind a corporate firewall.
var es = new EventSource(url, { proxy: 'http://your.proxy.com' });
The spec says that Eventsource
should reconnect when the connection errors. This is typically good behavior, but you might want to turn this off.
var es = new EventSource(url, { reconnect: false });
To work around the disadvantages of native Eventsource
, this module uses XHR long-polling to simulate an Eventsource
object. This can look like an idle connection to servers which can end the connection. This module will auto-reconnect, but if you'd like to avoid server errors, you can manually re-connect after a specified time.
// reconnect after 10 seconds
var es = new EventSource(url, { time: 10000 });