Many JavaScript or TypeScript developers don't think much about synchronization, even if they should. While it's true that JavaScript in Node.js or on the web is single-threaded, anytime an asynchronous function call is invoked, something else might be executed before control is handed back to your callback.
This library contains a classical set of high-quality synchronization primitives that can be used to protect critical sections in such code.
It's written in TypeScript (which means it provides excellent IDE/editor support out of the box) and down-compiled to
ES5, so it works equally well in Node.js or in any web browser (a Promise polyfill might be required, though).
Most synchronization primitives in this library has a "fair" counterpart, that requires the waiter to provide an ID token. The waiters are then woken up not in FIFO order but in such a way that each ID is processed before a waiter with a duplicate ID.
This section lists the synchronization primitives provided by this library.
Although not really a classical primitive, it's a fair queue based on the paper Efficient Fair Queuing Using Deficit Round-Robin. It's more or less just a TypeScript rewrite of Matt Lavin's drr-fair-queue.
This queue is the foundation of all the "fair" variants of the synchronization primitives.
A blocking queue (strict FIFO, or fair).
A condition variable implementation with notify(), notifyAll and wait() methods.
A trivial extension to the condition variable that allows a value to be passed to the waiter.
NOTE: Don't mistake this for a Pub/Sub primitive! While possible, it's very difficult to use these two primitives as event emitters without losing messages. See below instead.
A Pub/Sub primitive, with configurable capacity, blocking publishing and generator-based subscription, suitable to be
used in a for await-loop.
A classical semaphore that can be signaled and waited for. There is also a non-blocking take() method available.
Just a semaphore initialized to 1 and with more appropriate method names.
A few extra primitives taken more or less verbatim from the The Little Book of Semaphores by Allen B. Downey. There are no fair variants of these.