promise-order-execution.js

var q = require('q');
var fs = require('fs');

function test() {
  var deferred = q.defer();
  fs.readFile("package.json", "utf-8", function (error, text) {
      if (error) {
          deferred.reject(new Error(error));
      } else {
        setTimeout(function() {
          console.log('I am done! who is next?');
          deferred.resolve(text);
        }, 1500);
      }
  });

  return deferred.promise;
}

function test2() {
  var deferred = q.defer();
  test().then(deferred.resolve('before'));

  return deferred.promise;
}

function test3() {
  var deferred = q.defer();
  test().then(function () {
    deferred.resolve('after');
  });

  return deferred.promise;
}

function test4() {
  var deferred = q.defer();
  test().then(deferred.resolve);

  return deferred.promise;
}

test2().then(function (data) {
  console.log('This one calls ' + data + ' results coming');
});

test3().then(function (data) {
  console.log('This one calls ' + data + ' results coming');
});

test4().then(function (data) {
  console.log('This one calls after results with data from package.json ', data);
});

I've been using the

var deferred = q.defer();
...
if(x) {
  q.resolve(..); 
} else {
  q.reject(...);
}
return deferred.promise;

Pattern a lot until I read this: https://github.com/petkaantonov/bluebird/wiki/Promise-anti-patterns#the-deferred-anti-pattern

Now I try to avoid it, but I really don't know how to do that using Q. In private projects I use Bluebird which has a nice, terse syntax which I really like.

function isItAValidTime(currentTime, usingTimeSlots) {
  return new Promise(function(resolve, reject) {
    var theHour = currentTime.getHours();
    var day = currentTime.getDay();
    if (!usingTimeSlots || (theHour >= 5 && theHour < 8)) {
      resolve(true);
    } else {
      blinkPing();
      reject(new Error('Not in valid time slot'));
    }
  });
}

Do you know if you can do something similar in Q?