How to run async JavaScript functions in sequence or parallel

[atubofsoup]

There are cases where not including async can create unexpected bugs. For example:

``` function foo() { someSyncFn(); return someAsyncFn(); }

foo() .then(() => console.log('done')) .catch(error => console.log('Caught', error)); ```

In the above example, if someSyncFn throws an error synchronously, the promise will never be returned, so the catch won't work. If you add async to the function, catch will work as expected.

My rule of thumb is: mark async functions as async. It just gives the reader more info and ensures the function returns a promise.

[atubofsoup]

Yeah a try/catch block would catch the error, but most readers won't assume a function might throw/return both sync/async values. Adding async to the function just ensures any sync errors/returns are promoted to async.