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 readyState read-only property of the EventSource interface returns a number representing the state of the connection.
A number which is one of the three possible state constants defined on the EventSource interface:
EventSource.CONNECTING (0)The connection is not yet open.
EventSource.OPEN (1)The connection is open and ready to communicate.
EventSource.CLOSED (2)The connection is closed or couldn't be opened.
const evtSource = new EventSource("sse.php");
console.log(evtSource.readyState);
Note: You can find a full example on GitHub — see Simple SSE demo using PHP.
| Specification |
|---|
| HTML> # dom-eventsource-readystate-dev> |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | |
readyState |
6 | 79 | 6 | 12 | 5 | 18 | 45 | 12 | 5 | 1.0 | 4.4 | 5 |
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https://developer.mozilla.org/en-US/docs/Web/API/EventSource/readyState