Is there a way to short circuit async/await flow?

Question

async function update() {
   var urls = await getCdnUrls();
   var metadata = await fetchMetaData(urls);
   var content = await fetchContent(metadata);
   await rend         


        

Answer 1

Example written in Node with Typescript of a call which can be aborted from outside:

function cancelable(asyncFunc: Promise): [Promise, () => boolean] {
  class CancelEmitter extends EventEmitter { }

  const cancelEmitter = new CancelEmitter();
  const promise = new Promise(async (resolve, reject) => {

    cancelEmitter.on('cancel', () => {
      resolve();
    });

    try {
      await asyncFunc;
      resolve();
    } catch (err) {
      reject(err);
    }

  });

  return [promise, () => cancelEmitter.emit('cancel')];
}

Usage:

const asyncFunction = async () => {
  // doSomething
}

const [promise, cancel] = cancelable(asyncFunction());

setTimeout(() => {
  cancel();
}, 2000);

(async () => await promise)();