EventSource: open event

The open event of the EventSource API 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 like addEventListener(), or set an event handler property.

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

onopen = (event) => {};

Event type

A generic Event.

Examples

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

// addEventListener version
evtSource.addEventListener("open", (e) => {
  console.log("The connection has been established.");
});

// onopen version
evtSource.onopen = (e) => {
  console.log("The connection has been established.");
};

Specifications

Specification
HTML Standard # event-open
HTML Standard # handler-eventsource-onopen

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`open_event`	6	79	6	No	12	5	4.4	18	45	12	5	1.0

Docs

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