Adding async await without having to modify parent calling functions

Question

In my Javascript app I sometimes find I need to modify a section of code that is initially run synchronously and add some code that runs asynchronously.

Before:

function doSomething() {
   var x = 0;

   ...

   return true;
}

After:

async function doSomething() {
   var x = 0;
   await doSomethingElse();

   ...

   return true;
}

Many times this is fine. Problems occur however if the function doSomething is being called by another function that expects doSomething to complete and return a result. Originally the code was running synchronously, so this is not an issue. But now that I have added async to doSomething, it will return immediately even before the doSomethingElse call has completed. Yet I don't want doSomething to return until doSomethingElse has completed and any code following it. The only solution I can think of is to modify the calling code to handle doSomething as a Promise. The problem with this is that I end up having to do the same thing for the function that calls that function and so on up the hierarchy.

Is there a way to add the doSomethingElse in such a way that the doSomething will still execute synchronously?

A similar post seems to suggest that this is not possible (But that was 3 years ago. Maybe something has evolved since then to make it possible):

How to block for a javascript promise and return the resolved result?

it's still not possible and probably never will be. – Sandro Aug 01 '18 at 09:42 — Sandro, Aug 01 '18 at 09:42

score 0 · Answer 1 · answered Aug 01 '18 at 08:33

0

The only option you got is to "fire and forget" somewhen:

 function doSomething() {
   var x = 0;
   doSomethingElse();
    // ...
   return true;
}

answered Aug 01 '18 at 08:33

Jonas Wilms

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doSomethingElse returns a Promise and thus cannot be called as you have shown. – Johann Aug 01 '18 at 08:36
@androidDev oh really? – Jonas Wilms Aug 01 '18 at 08:43

score 0 · Answer 2 · answered Aug 01 '18 at 09:27

your doSomething method also return a promise.
So use it as normal promise

doSomething().then(boolean=>{

}).catch(e=>{

})

or

async function other(){
    try{
        let boolean = await doSomething();
        // your other code
    }catch(e){
        // your error handler
    }
}

Adding async await without having to modify parent calling functions

2 Answers2