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no-floating-broadcast-channels

Require BroadcastChannel handles to be retained so they can be closed.

Rule catalog ID: R011

Targeted pattern scopeโ€‹

This rule targets browser BroadcastChannel constructors:

  • BroadcastChannel
  • window.BroadcastChannel
  • self.BroadcastChannel
  • globalThis.BroadcastChannel

The rule reports channel instances that are immediately discarded or chained directly into a method call other than .close(). In both cases there is no remaining channel handle available for teardown.

What this rule reportsโ€‹

The rule reports:

  • standalone channel construction such as new BroadcastChannel("updates");
  • voided channel construction such as void new BroadcastChannel("updates");
  • immediate message sends such as new BroadcastChannel("updates").postMessage(message);
  • immediate listener registration on a discarded channel

It intentionally does not require same-function close() calls. Ownership can be transferred to a component instance, channel manager, returned value, or longer-lived runtime owner.

Why this rule existsโ€‹

BroadcastChannel.close() terminates the connection to the underlying channel and lets the browser know the channel is no longer needed. If the channel handle is discarded, code cannot reliably call .close() or remove listeners during cleanup.

Incorrectโ€‹

new BroadcastChannel("updates");
void new BroadcastChannel("updates");
new BroadcastChannel("updates").postMessage(message);
new BroadcastChannel("updates").addEventListener("message", onMessage);

Correctโ€‹

const channel = new BroadcastChannel("updates");

channel.addEventListener("message", onMessage);
channel.close();
return new BroadcastChannel(name);
registerChannel(new BroadcastChannel(name));

Behavior and migration notesโ€‹

Store the channel in the owner that will close it. For UI code, that is usually the component, route, or application shell lifecycle. For shared libraries, returning the channel or passing it to a channel manager keeps ownership explicit.

This rule does not autofix. Choosing the owner and close point is a semantic decision.

ESLint flat config exampleโ€‹

import runtimeCleanup from "eslint-plugin-runtime-cleanup";

export default [
    runtimeCleanup.configs.recommended,
];

When not to use itโ€‹

Do not enable this rule for code that intentionally creates application-lifetime channels and does not need explicit teardown. Prefer a narrow disable comment with a reason when a channel is meant to live for the whole runtime.

Further readingโ€‹