https://twitter.com/dnwiebe/status/1085509740095066113

retry_in_parallel.js

/*
 * testing involving real time is an integration test - high value, high cost
 * these next two routines represent that interface
 */
const msDeadline= ms=> {
  console.log('msDeadline',ms);
  const deadline= ms+new Date().getTime();
  return ()=>deadline < new Date().getTime();
};

const msDelay= ms=> {
  console.log('msDelay',ms);
  return new Promise(resolve => setTimeout(resolve, ms));
}

/*
 * here we use the type pun that non-zero integers are true
 * but you'll want something different:
 */

let attemptCount= 0;
const tryToConnect= async ()=> {
  const attempt= ++attemptCount;
  const s5= Math.sqrt(5);
  const delay= Math.pow((1+s5),20*Math.random())%s5;
  const success= 0.5<Math.random();
  console.log('tryToConnect',attempt,delay,success);
  await msDelay(delay);
  if (success) {
    return attempt;
  } else {
    throw new Error();
  }
}
 
/*
 * Try to connect every 250ms for two seconds,
 * and return me a Promise. If you connect,
 * resolve the Promise with true, if you fail until
 *  timeout, resolve it with false.
 */
const promiseToConnect= async ()=> {
  const pastDeadline= msDeadline(2000);
  let attempts= [];
  do {
    const pause= msDelay(250).then(()=>false);
    attempts.push(tryToConnect());
    try {
       const fileNumber= await Promise.race([pause].concat(attempts));
       if (fileNumber) return fileNumber;
    } catch (e) {
      await pause;
    }
  } while (!pastDeadline());
  return false;
}

let p= promiseToConnect();
p.then((ok)=>console.log('done', ok));