BroadcastChannel

Returns true when the runtime exposes BroadcastChannel. The API is available in every modern browser and requires no permissions.

var supported = await broadcastChannel.IsSupported();

Subscribes to a named channel. Every message arrives as a JsonElement so you can deserialize into whatever shape you expect; the optional onError callback fires on a messageerror event (a payload that could not be deserialized). One BroadcastChannel instance can host any number of named channels - the JS-side channel is created on first subscribe per name and torn down when its last subscription is disposed.

var subscription = await broadcastChannel.Subscribe("butil-demo",
    onMessage: data =>
    {
        // data is a JsonElement - e.g. data.GetString() for plain text
    },
    onError: () =>
    {
        // a message on the channel failed to deserialize
    });

// later, to detach:
await subscription.DisposeAsync();

Sends a message to every other listener on the channel within the same origin. Any JSON-serializable value works - strings, numbers or whole objects. Remember: the sender itself does not receive the message, so watch the console of the other tab.

await broadcastChannel.Post("butil-demo", "Hello, other tabs!");

// objects work too:
await broadcastChannel.Post("butil-demo", new { user = "alice", action = "signed-in" });