You can use below code for sleep function

1. /* time is in milliseconds - this is essentially a "sleep" function */  
2. wait: function(time){  
3.   var t1 = new GlideDateTime().getNumericValue();  
4.   var t2 = new GlideDateTime().getNumericValue();  
5.   var duration = t2 - t1;  
6.   while(duration < time){  
7.   t2 = new GlideDateTime().getNumericValue();  
8.   duration = t2 - t1;  
9.   }  
10. },  

from here: gs.sleep() in scoped application?

Regards,

Sachin