Add q-timeout to promises with either a value or callback

q-timeout.js

/**
 Example: timeout with message, just like Q.promise.timeout
 
  foo()
  .timeout(500, 'promise timed out!')
  .then(function () {
    console.log('foo has been resolved!');
  })
  .fail(function (msg) {
    console.log('failed with value:', msg);
  });

 Example: timeout with callback, reject deferred if you want

  foo()
  .timeout(500, function (defer) {
    console.log('timed out callback');
    defer.reject();
  })
  .fail(function (msg) {
    if (msg)
      console.log('failed with value:', msg);
  });
 */
var installed = false;

module.exports = function (q) {
  (function addPromiseTimeoutSupport(q) {
    if (installed) {
      return;
    }
    var _defer = q.defer;
    q.defer = function () {
      var d = _defer();
      d.promise.timeout = function (ms, timedOutValue) {
        setTimeout(function () {
          if (typeof timedOutValue === 'function') {
            timedOutValue(d);
          } else {
            d.reject(timedOutValue);
          }
        }, ms);
        return d.promise;
      };
      return d;
    };
    installed = true;
  }(q));
};

I always wanted to run a callback on promise timeout. Q.promise.timeout is almost what I needed, this adds ability to run a dedicated callback. One still needs to detect if the promise was rejected due to timeout in .fail callback.