CallbackWithTeardown - API reference

API reference › @evolu/common › Types › CallbackWithTeardown

type CallbackWithTeardown<T> = (value: T) => void | (() => void);

Defined in: packages/common/src/Types.ts:73

A function that receives a value and optionally returns a teardown function.

Use for subscriptions or callbacks that need abort-time teardown.

Subscription teardown

import { assertEqual, type CallbackWithTeardown } from "@evolu/common";

interface EventSource {
  readonly start: () => void;
  readonly stop: () => void;
}

const events: Array<string> = [];
const source: EventSource = {
  start: () => {
    events.push("started");
  },
  stop: () => {
    events.push("stopped");
  },
};
const subscribe: CallbackWithTeardown<EventSource> = (source) => {
  source.start();
  return source.stop;
};
const teardown = subscribe(source);
if (teardown) teardown();

assertEqual(events, ["started", "stopped"]);