EventSource: EventSource() constructor

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

Note: This feature is available in Web Workers.

The EventSource() constructor returns a newly-created EventSource, which represents a remote resource.

Syntax

js
new EventSource(url)
new EventSource(url, options)

Parameters

url

A string that represents the location of the remote resource serving the events/messages.

options Optional

Provides options to configure the new connection. The possible entries are:

withCredentials Optional

A boolean value, defaulting to false, indicating if CORS should be set to include credentials.

Examples

js
const evtSource = new EventSource("sse.php");
const eventList = document.querySelector("ul");

evtSource.onmessage = (e) => {
  const newElement = document.createElement("li");

  newElement.textContent = `message: ${e.data}`;
  eventList.appendChild(newElement);
};

Note: You can find a full example on GitHub — see Simple SSE demo using PHP.