Is increment an atomic operation in JavaScript?

Javascript is single threaded, So you need to worry about deallocks or dirty read problems. Why doesn't JavaScript support multithreading?

In JavaScript, a function always runs to completion. That means if a function is running, then it will run completely; only after that, the other function will be called. So, there is no chance of interleaving between statements (but in case of Java it is different).

If you are confused with asynchronous execution, then always remember async means later not parallel. So, coming to your problem, the answer is, No you will not face any problem, it will be a total atomic operation.

Javascript does not support multithreading. It may have web workers, but your question would not apply to this case, as workers do not share variables.