There are a few different nuances to this question.

Can it be done? sure:

   let bar = await foo();
   return bar + 1;

can be converted to:

   let resultPromise = foo();
   while (!resultPromise.isComplete()){
       sleep(10);
   }
   let bar = resultPromise.value();
   return bar + 1;

the issue is that this is terribly inefficient as you are asking every 10ms whether or not the result is ready.

One of the reasons this is so inefficient is that you have to spend time checking (which is wasteful if it isnt ready) and waiting. If you check more frequently, you're wasting CPU. If you spend more time waiting, you can waste up to that much time if the result is ready right after you go to sleep.

The alternative is to have the operating system tell you when its ready. This is done through the event loop. So this would turn the code transformation into something like the following:

  let resultPromise = foo().then(function(bar){
     return bar + 1;
  });
  

but what do you return? you have to return a promise (i.e. a callback). Therefore, all callers of this function have to be ready to handle this.