AsyncDisposableStack.prototype.defer()

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The defer() method of AsyncDisposableStack instances takes a callback function to be called and awaited when the stack is disposed.

See DisposableStack.prototype.defer() for general information about the defer() method.

Syntax

js
defer(onDispose)

Parameters

onDispose

A function that will be called when the stack is disposed. The function receives no arguments and can return a promise which gets awaited.

Return value

None (undefined).

Exceptions

TypeError

Thrown if onDispose is not a function.

ReferenceError

Thrown if the stack is already disposed.

Examples

Using defer()

One use case of defer() is to do something unrelated to resource freeing during scope exit, such as logging a message.

js
async function doSomething() {
  await using disposer = new AsyncDisposableStack();
  disposer.defer(async () => {
    await fs.writeFile("log.txt", "All resources freed successfully");
  });
  // Other code that claims and frees more data
}

Specifications

Specification
ECMAScript Async Explicit Resource Management
# sec-asyncdisposablestack.prototype.defer

Browser compatibility

desktop mobile server
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Bun
Deno
Node.js
defer
Chrome – Full support
Chrome 134 (Release date: 2025-03-04)
footnote Full support
Edge – Full support
Edge 134 (Release date: 2025-03-06)
footnote Full support
Firefox – Full support
Firefox 141 (Release date: 2025-07-22)
footnote Full support
Opera – Full support
Opera 119 (Release date: 2025-05-13)
footnote Full support
Safari – No support
Safari
footnote No support
Chrome Android – Full support
Chrome Android 134 (Release date: 2025-03-04)
footnote Full support
Firefox for Android – Full support
Firefox for Android 141 (Release date: 2025-07-22)
footnote Full support
Opera Android – Full support
Opera Android 88 (Release date: 2025-03-19)
footnote Full support
Safari on iOS – No support
Safari on iOS
footnote No support
Samsung Internet – Full support
Samsung Internet 29 (Release date: 2025-10-25)
footnote Full support
WebView Android – Full support
WebView Android 134 (Release date: 2025-03-04)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
Bun – Full support
Bun 1.3 (Release date: 2025-10-10)
footnote Full support
Deno – Full support
Deno 2.2.10 (Release date: 2025-04-15)
footnote Full support
Node.js – Full support
Node.js 24 (Release date: 2025-05-06)
footnote Full support

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support

See also