EventSource: open 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.

Note: This feature is available inWeb Workers.

Theopen event of theEventSource interface is fired when a connection with an event source is opened.

This event is not cancelable and does not bubble.

Syntax

Use the event name in methods likeaddEventListener(), or set an event handler property.

addEventListener("open", (event) => { })onopen = (event) => { }

Event type

A genericEvent.

Examples

const evtSource = new EventSource("sse.php");// addEventListener versionevtSource.addEventListener("open", (e) => {  console.log("The connection has been established.");});// onopen versionevtSource.onopen = (e) => {  console.log("The connection has been established.");};