AsyncDisposableStack.prototype.adopt()

The adopt() method of AsyncDisposableStack instances registers a value that doesn't implement the async disposable protocol to the stack by providing a custom disposer function.

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

Syntax

js
adopt(value, onDispose)

Parameters

value

Any value to be registered to the stack.

onDispose

A function that will be called when the stack is disposed. The function receives value as its only argument, and it can return a promise which gets awaited.

Return value

The same value that was passed in.

Exceptions

TypeError

Thrown if onDispose is not a function.

ReferenceError

Thrown if the stack is already disposed.

Examples

undefined

Using adopt()

This function creates a file handle (as a Node.js FileHandle), that gets closed when the function completes. We suppose that the file handle does not implement the async disposable protocol (in reality it does), so we use adopt() to register it to the stack. Because the handle.close() method returns a promise, we need to use an AsyncDisposableStack so that the disposal gets awaited.

js
async function readFile(path) {
  await using disposer = new AsyncDisposableStack();
  const handle = disposer.adopt(
    await fs.open(path),
    async (handle) => await handle.close(),
  );
  const data = await handle.read();
  // The handle.close() method is called and awaited here before exiting
  return data;
}

Specifications

See also