Promises example: Race to success

main.js

// Logging helpers

var _startTime;

function _log() { // calling: _log.apply(console.log, arguments);
  var nowTime = new Date();
  var args = Array.prototype.slice.call(arguments, 0);
  // var log = args.pop();
  if (!_startTime) _startTime = nowTime;
  args.unshift(('    ' + (nowTime - _startTime)).slice(-5), 'ms:');
  this(args.join(' '));
}

function logInfo() {
  _log.apply(console.log, arguments);
}

function logError() {
  _log.apply(console.error, arguments);
}

// --------------------

function mockRequest(result, timeout, success) {
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      if (success) {
        logInfo('+++ Resolving promise [' + result + ']');
        resolve(result)
      } else {
        logInfo('xxx Rejecting promise [' + result + ']');
        reject(result);
      };
    }, timeout);
  });

}

function invertPromise(promise) {
  return new Promise(function (resolve, reject) { promise.then(reject, resolve); });
}

function raceToSuccess(promises) {
  return invertPromise(Promise.all(promises.map(invertPromise)));
}

// --------------------

function _mockRequest(result, timeout, success) {
  var p;
}

logInfo('Starting...');
// mockRequest('Request 01 succeded', 500, true).then(logInfo, logError);
// mockRequest('Request 02 failed', 550, false).then(logInfo, logError);
// invertPromise(mockRequest('Request 03 succeded inverted', 600, true)).then(logInfo, logError);
// invertPromise(mockRequest('Request 04 failed inverted', 650, false)).then(logInfo, logError);

var requests = [];
var success;
var timeout = 0;

for (var i = 0; i < 5; ++i) {
  success = Math.random() >= .5;
  timeout += Math.round(Math.random() * 50 + 1) * 10;
  requests.push(mockRequest('Request ' + ('0' + (i + 1)).slice(-2) + (success ? ' succeded' : ' failed') + '.', timeout, success));
  console.log('Request ' + ('0' + (i + 1)).slice(-2) + ' will be' + (success ? ' succeded' : ' failed') + ' in ' + timeout + ' ms.');
}

raceToSuccess(requests).then(logInfo, logError);