JS has concurrency (but not parallelism) despite being single-threaded, though.
If you ever put an await anywhere in your code, an arbitrary amount of random stuff might run between the time you await and the time the awaiting finishes.
Same applies to older mechanisms like callbacks and promises.
Race conditions are more rare there because as long as you aren't doing any IO, there is indeed no concurrency, so you can't e.g. get two threads trying to increment a single variable at the same time. They can still happen, though, especially if you accidentally do a partial change to an object, put it in an illegal state, and do IO before you finish that change.
If you ever put an await anywhere in your code, an arbitrary amount of random stuff might run between the time you await and the time the awaiting finishes.
Same applies to older mechanisms like callbacks and promises.
Race conditions are more rare there because as long as you aren't doing any IO, there is indeed no concurrency, so you can't e.g. get two threads trying to increment a single variable at the same time. They can still happen, though, especially if you accidentally do a partial change to an object, put it in an illegal state, and do IO before you finish that change.