deferAsync

Creates an AsyncDisposable object that runs an asynchronous callback when its scope exits.

await using cleanup = deferAsync(callback);

Usage

deferAsync(callback)

Use deferAsync when you want asynchronous cleanup code to run automatically at the end of a scope. Declare the returned object with an await using declaration, and the callback runs and is awaited when the enclosing block exits — even if it exits with an error.

import { deferAsync } from 'es-toolkit/util';

async function main() {
  const connection = await connect();
  await using cleanup = deferAsync(async () => {
    await connection.close();
  });

  // The connection is closed automatically when this function returns or throws.
  await connection.query('SELECT 1');
}

await using declarations require TypeScript 5.2 or later, and a runtime that supports Explicit Resource Management, such as Node.js 24 or the latest browsers. In older environments, you can transpile the syntax and polyfill Symbol.asyncDispose.

::: info Use defer for synchronous cleanup

This function awaits the callback, so it can only be used in async functions. If your cleanup code is synchronous, use the defer function with using instead.

:::

Parameters

• callback (() => void | PromiseLike<void>): The cleanup function to run when the object is disposed. Its result is awaited.

Returns

(AsyncDisposable): An object that runs and awaits callback when it is disposed.