AsyncDisposableStack.prototype.defer()

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

See {{jsxref("DisposableStack.prototype.defer()")}} for general information about the defer() method.

Syntax#

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 ({{jsxref("undefined")}}).

Exceptions#

• {{jsxref("TypeError")}}
• : Thrown if onDispose is not a function.
• {{jsxref("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.

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#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• JavaScript resource management
• {{jsxref("AsyncDisposableStack")}}
• {{jsxref("AsyncDisposableStack.prototype.adopt()")}}
• {{jsxref("AsyncDisposableStack.prototype.use()")}}