EventSource: error event

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.

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Note: This feature is available in Web Workers.

The error event of the EventSource API is fired when a connection with an event source fails to be opened.

This event is not cancelable and does not bubble.

Syntax

Use the event name in addEventListener():

addEventListener("error", (event) => { })

Alternatively, assign to the event handler property of the interface:

onerror = (event) => { }

Event type

A generic Event.

Examples

const evtSource = new EventSource("sse.php");

// addEventListener version
evtSource.addEventListener("error", (e) => {
  console.log("An error occurred while attempting to connect.");
});

// onerror version (but note that this replaces other event listeners
// added using onerror, if any)
evtSource.onerror = (e) => {
  console.log("An error occurred while attempting to connect.");
};