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

BCD tables only load in the browser

See also