A simple implementation of a "race" callback pattern such that the first one of an array `entries` callbacks to either resolve or reject determines the overall result

callbackRace.js

var once = function (func) {
  var done = false;
  return function (res) {
    if (done) return;
    if (res) {
      func.apply(this, arguments);
    } else {
      func.apply(this, false);
    }
    done = true;
  }
}

function race (entries, cb) {
 var onceCB = once(cb);
 entries.map(entry => { entry(data, onceCB) });
}