> If the threads and their scheduling are implemented wholly by the language There's just one thread, one event loop, for all of JavaScript... so we're not tal

> If the threads and their scheduling are implemented wholly by the language There's just one thread, one event loop, for all of JavaScript... so we're not talking about true thread-level race conditions. > strongly implying that it takes unusual conditions for events to lag significantly As far as expectations of software running inside of web pages, it is in fact quite exceptional for there to be significant delays between when you expect for something to happen and when it actually happens. For example, if I set up a timer for 953ms from now, and it actually runs at 3953ms from now, that extra 3 seconds is extremely uncommon for the UX expected on the web. I think the disconnect here is that you're really asserting things about what happens at the OS level, where multiple threads and real I/O are happening, etc. I'm entirely talking about JavaScript, which is single-threaded, and where asynchrony is just simple event-loop concurrency (interleaving actions). It means that two timers should, in simplest terms, order themselves according to normal expectations. It'd be unusual for there to be significant deviations.