How to 'return' outside function definition in typescript

1. 
   

   I need to rewrite my tampermonkey script on typescript.

   
   


2. 
   

   What is correct way to rewrite this javascript on typescript?

   
   

   
   if (window.top != window.self ) {
       return;
   }
   
   

Main goal is to stop executing script if it's running not in window.top.

Typescript compiler write ERROR TS1108: A 'return' statement can only be used within a function body.