Question

are there any javascript libraries which provide promises and futures syntactically similar to that of C++ ones. basically we want to use them in webworkers, I dont want a callback interface. I want the webworker to block on a future and continue when the UI thread sets the value of the future. i have looked at every possible promise and future library but every thing expects a callback, our code is already a mess and we dont want to further complicate it.

Answer 1

http://code.google.com/p/google-caja/source/browse/trunk/src/com/google/caja/ses-promise.js

Implementation of promises for SES/ES5. Exports Q to the global scope.

Mostly taken from the ref_send implementation by Tyler Close, with the addition of a trademark table to support promises for functions.

Btw, Mark Miller is working on codifying JavaScript’s concurrency model and adding eventual send semantics with syntactic sugar for a future version of the language. From http://wiki.ecmascript.org/doku.php?id=strawman:concurrency

1. Reality: Codifying and formalizing JavaScript’s de-facto concurrency model as a de-jure model.
2. Promises: A way to (Q(p).post(), Q(p).get()) Make asynchronous requests of objects that may not be synchronously reachable, such as remote objects. (Q(p).when()) Ease the burden of local event loop programming, by reifying the ability to register a callback as a first class value. (Q.async, yield:) for implicit registration of shallow continuations on promises.
3. Syntactic sugar. The infix “!” operator: An eventual analog of “.“, for making eventual requests look more like immediate requests.
4. (Q.makePromise()) A promise extension mechanism, so that promise handlers can turn local promise operations into remote messages.
   Transport independence: Using remote object messaging as a symmetric abstraction layer, hiding the annoying differences among the various transports listed above as well as server-to-server TCP and UDP transports.
5. (Vat()) An event-loop spawning mechanism for spawning new event loops that run concurrently with the event loop which spawned it.
   Worker independence: Using Vat API as an abstraction layer around worker spawning on the browser or process spawning on the server.
6. (Vat.evalLater(), where()) Using JavaScript itself as mobile code, so event loops can safely inject new behavior into other event loops
   Symmetric Mobile Code: Generalizes from the current use of JavaScript as mobile code sent only from server and only to browsers.
   Async-PGAS: Provides a distributed analog to the expressiveness of The Asynchronous Partitioned Global Address Space Model.