What is executed (explicitly and implicitly) in parallell and what sequentially in node.js?

This example confuse my understanding of how the node.js works:

// 1.
numbers.forEach(function(number) {
  queue.push(Q.call(slowFunction, this, number));
});

// 2.
// Q.all: execute an array of 'promises' and 'then' call either a resolve 
// callback (fulfilled promises) or reject callback (rejected promises)
Q.all(queue).then(function(ful) {

  // All the results from Q.all are on the argument as an array
  console.log('fulfilled', ful);
}, function(rej) {

  // The first rejected (error thrown) will be here only
  console.log('rejected', rej);
}).fail(function(err) {

  // If something went wrong, then we catch it here, usually when there is no
  // rejected callback.
  console.log('fail', err);
}).fin(function() {

  // Finally statement; executed no matter of the above results
  console.log('finally');
});

Why it is assumed here, that 1. and 2. parts of code will be executed sequentially? So, where is the guarantee that Q.all(queue) works on all queue elements pushed in 1.? Could it be so, that the numbers from 1. is so big, that it works than parallel to 2.? These ideas coming from the understanding that node.js will handling 1. and 2. first of all with the node.js event-loop and then give it to workers, which are actually analogue to the normal threads.

So the question - will be 1. and 2. executed parallel to each other, started from node.js event-loop sequentially or will they be executed sequentially (the 1. push all elements in the queue and only after that the 2. starts to handling each element in the queue) ? Please provide arguments with some direct links to documentation for this topic.