I need to execute 2 functions one after the other with the stuff in function "A" fully completing before the stuff in function "B" executes...

I can't find an example that is not using setTimeout .. which is strange ...

I have the  following example below ( from here ) , is it supposed to work ?? How could I test if it is working ? what dummy code could I use to simulate the part  //do stuff with SharePoint JSOM taking 5 secs to 30 secs ,say ... 

1. 
   
2. var a = function() {
3.     var defer = $.Deferred();
4.       
5. //do stuff with SharePoint JSOM
6. 
   
7.     console.log('a() called');
8.     defer.resolve();
9.     return defer;
10. };
11. 
    
12. var b = function() {
13.     var defer = $.Deferred();
14. 
    
15.     console.log('b() called');
16. 
    
17.     defer.resolve();
18.     return defer;
19. };
20. 
    
21. 
    
22. 
    
23. a().then(b);