Deadlocks can happen in any kind of concurrent system with locks. As soon as you start building & using locks with Promises, this is quite easy to happen. That

Deadlocks can happen in any kind of concurrent system with locks. As soon as you start building & using locks with Promises, this is quite easy to happen. That said, the need for locks in JavaScript is much less than in a typical multi-threaded language, so it's a lot easier to keep track of and avoid deadlocks, if you're even using locks at all.