BroadcastChannel.onmessage 在 Firefox 中不起作用

Question

I need to share some information between 2 tabs of the same browser pointing at the same site. I'm using the BroadcastChannel.onmessage event handler as detailed here: https://developer.mozilla.org/en-US/docs/Web/API/BroadcastChannel/onmessage

In the sender tab javascript code I defined:

var bc = new BroadcastChannel('my_bc_channel');
bc.postMessage(i); //where i is simply the line number i want to share

And in the receiving tab:

var bc = new BroadcastChannel('my_bc_channel');
//then use this to receive the incoming messages:
bc.onmessage = function (ev) {
    last_line = ev.data
}

My code works fine in Chrome, but it does not do anything in Firefox (latest version 70 freshly installed under windows). The compatibility chart in the link I gave above says it should be working from Firefox version 38.

The thing is, I'm not sure how to debug this. I don't have any error messages in the console. I don't know if it's the sender code that does not send anything. But clearly the receiving code is not triggered so I guess the .onmessage event is not detected. Where can I see in the javascript console if the message is sent ?

Answer 1

I opened a bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1600512

Seems BroadcastChannel.onmessage does not work properly when you host your files locally on your hard drive, as I did in my example above. It works otherwise.

Answer 2

It might be that the channel "in the receiving tab" has it's onmessage handler set only after the other tab has broadcast the message, and the message is lost.

You might want the "sending" tab to also set a message handler, and wait for the other tab to broadcast a message that it is ready to receive, and only then start the broadcast.