Can someone explain why they didn’t go with (anonymous) class destructors? Or something other than a Symbol as special object key. Especially when there are two Symbols (different one for asynchronous) which makes it a leaky abstraction, no?
Hence many either had or ended up growing means of lexical (scope-based) resource cleanup whether,
- HoF-based (smalltalk, haskell, ruby)
- dedicated scope / value hook (python[1], C#, Java)
- callback registration (go, swift)
[1]: Python originally used destructors thanks to a refcounting GC, but the combination of alternate non-refcounted implementations, refcount cycles, and resources like locks not having guards (and not wanting to add those with no clear utility) led to the introduction of context managers
E.g. in Ruby you can lock/unlock a mutex, but the normal way to do it would be to pass a block to `Mutex#synchronize` which is essentially just
def synchronize
lock
begin
yield
ensure
unlock
end
end
lock.synchronize {
# protected code here
}The dispose methods on the other hand are called when the variable goes out of scope, which is much more predictable. You can rely on for example a file being closed ot a lock released before your method returns.
JavaScript is already explicit about what is synchronous versus asynchronous everywhere else, and this is no exception. Your method needs to wait for disposing to complete, so if disposing is asynchronous, your method must be asynchronous as well. It does get a bit annoying though that you end up with a double await, as in `await using a = await b()` if you're not used to that syntax.
As for using symbols - that's the same as other functionality added over time, such as iterator. It gives a nice way for the support to be added in a backwards-compatible way. And it's mostly only library authors dealing with the symbols - a typical app developer never has to touch it directly.
https://waspdev.com/articles/2025-04-09/features-that-every-... https://waspdev.com/articles/2025-04-09/features-that-every-...
But even Mozilla doesn't recommend to use them because they're quite unpredictable and might work differently in different engines.