RestServices.options

Performs a REST HTTP OPTIONS call and returns the HTTP response code. Returns a RestResponse representing the response.

Example:

 var uri = "http://example.com/rest/users";
 //create authentication 
 var auth = HttpAuthentication.createBasicAuthentication("username", "password");
 var opts = new RestOptions();
 //setting the wait time to establish a connection to the target server to 5 seconds
 opts.setConnectionTimeout(5);
 //set the time to wait for no inactivity from the rest call to 10 seconds
 opts.setSocketTimeout(10);
 var response = services.rest.options(uri, auth, opts);
 if(response.isSuccess())
 {
   var allowed = response.getHeaders()['Allow'];
   if(allowed)
   {
     var results = allowed.split(',');
     var list = fields.options.createCustomList();
     for each(var x in results)
     {
        list.add(x);
     }
   }
 }
 

Further documentation.