Virtually all real-world stacks I know of use a work queue where each element in the list is queued up once it's ready. You don't need on-stack recursion or unbounded memory to track the execution states.
It's pretty trivial to implement this given a promises API and any sort of event queue, but you could also just do it with callbacks. So in the browser you'd literally just use setTimeout.
One reason this is so common is that it's trivial to end up blowing out the stack with recursive IO callbacks, because sometimes all your read()s complete instantly because all the data's in cache. Oops!
It's pretty trivial to implement this given a promises API and any sort of event queue, but you could also just do it with callbacks. So in the browser you'd literally just use setTimeout.
One reason this is so common is that it's trivial to end up blowing out the stack with recursive IO callbacks, because sometimes all your read()s complete instantly because all the data's in cache. Oops!