iter-tools-es/impls/async-interleave-ready/internal/race-to.js

The iterable toolbox

function raceTo(predicate, notFoundValue, promises) {
  return new Promise((resolve, reject) => {
    let promiseCount = 0;
    let settledPromiseCount = 0;
    let resolved = false;
    let rejected = false;

    for (const promise of promises) {
      promise.catch(error => {
        if (!rejected && !resolved) {
          reject(error);
          rejected = true;
        }
      }).then(result => {
        settledPromiseCount++;

        if (!resolved && !rejected) {
          if (predicate(result)) {
            resolve(result);
            resolved = true;
          } else if (settledPromiseCount === promiseCount) {
            resolve(notFoundValue);
          }
        }
      });
      promiseCount++;
    }
  });
}

exports.raceTo = raceTo;