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MessagePort: messageerror event
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2023.
The messageerror event is fired on a MessagePort object when it receives a message that can't be deserialized.
This event is not cancellable and does not bubble.
A common cause of messageerror events is attempting to send a SharedArrayBuffer object, or a buffer view backed by one, across agent clusters. For example, a window is not in the same agent cluster as a shared worker it created, so suppose the page runs the following code:
js
const worker = new SharedWorker("worker.js");
worker.port.start();
worker.port.addEventListener("message", (event) => {
worker.port.postMessage(new SharedArrayBuffer(1024));
});
And worker.js contains the following code:
js
self.addEventListener("connect", (event) => {
console.log("Hello");
const port = event.ports[0];
port.start();
port.postMessage("Port connected");
port.addEventListener("messageerror", (event) => {
console.log("Message error");
});
});
Then the shared worker will receive a messageerror event when it tries to deserialize the message sent from the window.
Note:
You can use browser devtools to debug your SharedWorker, by entering a URL in your browser address bar to access the devtools workers inspector; for example, in Chrome, the URL chrome://inspect/#workers, and in Firefox, the URL about:debugging#workers.