Baseline Widely available
Note: This feature is only available in Service Workers.
The ExtendableMessageEvent interface of the Service Worker API represents the event object of a message event fired on a service worker (when a message is received on the ServiceWorkerGlobalScope from another context) â extends the lifetime of such events.
This interface inherits from the ExtendableEvent interface.
ExtendableMessageEvent()
Creates a new ExtendableMessageEvent object instance.
Inherits properties from its parent, ExtendableEvent.
ExtendableMessageEvent.data Read only
Returns the event's data. It can be any data type. If dispatched in messageerror event, the property will be null.
ExtendableMessageEvent.origin Read only
Returns the origin of the Client that sent the message.
ExtendableMessageEvent.lastEventId Read only
Represents, in server-sent events, the last event ID of the event source.
ExtendableMessageEvent.source Read only
Returns a reference to the Client object that sent the message.
ExtendableMessageEvent.ports Read only
Returns the array containing the MessagePort objects representing the ports of the associated message channel.
Inherits methods from its parent, ExtendableEvent.
In the below example a page gets a handle to the ServiceWorker object via ServiceWorkerRegistration.active, and then calls its postMessage() function.
// in the page being controlled
if (navigator.serviceWorker) {
navigator.serviceWorker.register("service-worker.js");
navigator.serviceWorker.addEventListener("message", (event) => {
// event is a MessageEvent object
console.log(`The service worker sent me a message: ${event.data}`);
});
navigator.serviceWorker.ready.then((registration) => {
registration.active.postMessage("Hi service worker");
});
}
The service worker can receive the message by listening to the message event:
// in the service worker
addEventListener("message", (event) => {
// event is an ExtendableMessageEvent object
console.log(`The client sent me a message: ${event.data}`);
event.source.postMessage("Hi client");
});
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