ExtendableMessageEvent.lastEventId

The lastEventID read-only property of the ExtendableMessageEvent interface represents, in server-sent events, the last event ID of the event source. This is an empty string.

Value

A string.

Examples

When the following code is used inside a service worker to respond to a push messages by sending the data received via PushMessageData to the main context via a channel message, the event object of onmessage will be a ExtendableMessageEvent.

let port;

self.addEventListener('push', (e) => {
  const obj = e.data.json();

  if (obj.action === 'subscribe' || obj.action === 'unsubscribe') {
    port.postMessage(obj);
  } else if (obj.action === 'init' || obj.action === 'chatMsg') {
    port.postMessage(obj);
  }
});

self.onmessage = (e) => {
  console.log(e.lastEventId);
  port = e.ports[0];
}

Specifications

Specification
Service Workers
# extendablemessage-event-lasteventid

Browser compatibility

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See also