I'm using this library to chain asynchronous functions in my nodejs app:

var chain = async(function(){

    var foo = await(bar());
    var foo2 = await(bar2());
    var foo3 = await(bar2());

}

So bar3 waits for bar2 to finish and bar2 waits for bar() to finish. That's fine. But what will I do in order to stop the async block from further execution? I mean something like this:

var chain = async(function(){

    var foo = await(bar());
    if(!foo){return false;} // if bar returned false, quit the async block
    var foo2 = await(bar2());
    var foo3 = await(bar2());

}

what's the best approach to handle this?

at the moment I throw an exception within bar and handle the exception in way:

chain().catch(function (err) { //handler, ie log message)

It's working, but it doesn't look right

I'm using this library to chain asynchronous functions in my nodejs app: https://github./yortus/asyncawait

var chain = async(function(){

    var foo = await(bar());
    var foo2 = await(bar2());
    var foo3 = await(bar2());

}

So bar3 waits for bar2 to finish and bar2 waits for bar() to finish. That's fine. But what will I do in order to stop the async block from further execution? I mean something like this:

var chain = async(function(){

    var foo = await(bar());
    if(!foo){return false;} // if bar returned false, quit the async block
    var foo2 = await(bar2());
    var foo3 = await(bar2());

}

what's the best approach to handle this?

at the moment I throw an exception within bar and handle the exception in way:

chain().catch(function (err) { //handler, ie log message)

It's working, but it doesn't look right

• javascript
• node.js
• async-await
• ecmascript-2016

• Doesn't return false as you wrote it just work? – Bergi Commented Mar 3, 2015 at 16:32

2 Answers 2

I mean something like this …

asyncawait supports exactly this syntax. Just return from the function:

var chain = async(function(){
    var foo = await(bar());
    if (!foo) return;
    var foo2 = await(bar2());
    var foo3 = await(bar2());
});

As an alternative to the accepted answer, and depending on your usage, you may want your bar()s to throw/reject.

async function bar() {
  try {
    Api.fetch(...) // `fetch` is a Promise
  } catch (err) {
    // custom error handling
    throw new Error() // so that the caller will break out of its `try`

    // or re-throw the error that you caught, for the caller to use
    throw err
  }

  // or, instead of a try/catch here, you can just return the Promise
  return Api.fetch(...)
}

var chain = async(function(){
  try {
    // if any of these throw or reject, we'll exit the `try` block
    var foo = await(bar());
    var foo2 = await(bar2());
    var foo3 = await(bar2());
  } catch {} // ES2019 optional catch. may need to configure eslint to be happy
});