DisposableStack.prototype.defer() - JavaScript | MDN
Syntax
Parameters
onDispose-
A function that will be called when the stack is disposed. The function receives no arguments.
Return value
None (undefined).
Exceptions
TypeError-
Thrown if
onDisposeis not a function. ReferenceError-
Thrown if the stack is already disposed.
Description
The primary purpose of defer() is to register a cleanup callback that's not specific to the disposal of a particular resource. If the callback is specific to a resource, you should use use() or adopt() instead. You can also use defer when the resource is not claimed within your code:
js
function consumeReader(reader) {
using disposer = new DisposableStack();
disposer.defer(() => reader.releaseLock());
// Do something with reader
}
Examples
Using defer()
This function sets a simple lock to prevent multiple async operations from running at the same time. The lock is released when the function completes.
js
let isLocked = false;
async function requestWithLock(url, options) {
if (isLocked) {
return undefined;
}
using disposer = new DisposableStack();
isLocked = true;
disposer.defer(() => (isLocked = false));
const data = await fetch(url, options).then((res) => res.json());
return data;
}
Specifications
| Specification |
|---|
| ECMAScript Async Explicit Resource Management # sec-asyncdisposablestack.prototype.defer |