I've found an example for selecting time spans of working hours of a certain user. It's found in the SDK but, given that the example is written as a console application in C#, it might be perceived as complicated an unnecessarily complicated.
Also, it's mentioned that there's a field on the user entity, I assume that for this particular task, JavaScript might be more suitable and such an example I haven't seen.
This page presenting the source code is on MSDN. The bottom line is that you create a service and then execute the below.
QueryScheduleRequest scheduleRequest = new QueryScheduleRequest
{
ResourceId = GetRegardedUserId(),
Start = DateTime.Now,
End = DateTime.Today.AddDays(14),
TimeCodes = new TimeCode[] { TimeCode.Available }
};
QueryScheduleResponse scheduleResponse
= (QueryScheduleResponse)_serviceProxy.Execute(scheduleRequest);
For more information on how to handle the requests to scheduling and working hours see this article and for service appointments look over here.