Thread-safe array deletions
javascript
Solution
Regarding your precise question: No, you can't have concurrency problem as JavaScript isn't multithreaded. Even if you use webworkers you won't have problems as no data is shared (workers communicate by passing messages). Even in node.js your script isn't multi-threaded. There's no way that a parallel execution does anything during the execution of your function unless you use `await`.
So simply use `splice`, there is no need to lock the array.
Regarding concurrency problems more generally, you should be aware that, as soon as you use `await`, the execution can be cut in chunks and another function can run while you're awaiting. `splice` will never be cut but be careful to the logic of your algorithm on shared data when you're in an `async` function.
Problem
I know one can either `splice` an item out of an array, or delete it with `delete`. The former approach can cause concurrency problems, e.g. if one thread is walking over the array while another has just shifted or spliced. `delete` doesn't have this issue if `forEach` is used on the array, since `forEach` will walk over holes in the array. However, the array can't keep growing forever and will necessitate sweeping, potentially causing the same issue as in the case of a splice. Sounds like I need locking, but I'd be amused if Javascript had any facilities for it. Any thoughts?