Parallel implementation

//implement missing "Parallel" please
//try to do so with a minimal amount of code

//implementation
function Parallel({paralelJob}) {
  this.paralelJob = paralelJob;
  this.results = [];
  this.calledCounter = 0;
  this.totalCounter = 0;
}

Parallel.prototype.done = function(callback) {
  setTimeout(function tick(self) {
    if (!self.calledCounter) {
      callback(self.results);
    } else {
      setTimeout(tick, 0, self);
    }
  }, 0, this);
}

Parallel.prototype.complete = function complete(counter, result) {
console.log(result + ' completed')
this.results[counter] = result;
  --this.calledCounter;
};

Parallel.prototype.job = function job(callback) {
  setTimeout(function jobApply(self){
  if (self.calledCounter < self.paralelJob) {
    callback(self.complete.bind(self, self.totalCounter++));
    ++self.calledCounter;
  } else {
    setTimeout(jobApply, 0, self)
  }}, 0, this);
  return this;
};


//check calls

var runner = new Parallel({
  paralelJob: 2
});

runner.job(step1)
  .job(step2)
  .job(step3)
  .job(step4)
  .done(onDone);

function step1(done) {
  console.log('step1');
  setTimeout(done, 100, 'step1');
}

function step2(done) {
  console.log('step2');
  setTimeout(done, 10, 'step2');
}

function step3(done) {
  console.log('step3');
  setTimeout(done, 150, 'step3');
}

function step4(done) {
  console.log('step4');
  setTimeout(done, 50, 'step4');
}

function onDone(results) {
console.log(results);
  console.assert(Array.isArray(results), 'expect result to be array');
  console.assert(results[0] === 'step1', 'Wrong answer 1');
  console.assert(results[1] === 'step2', 'Wrong answer 2');
  console.assert(results[2] === 'step3', 'Wrong answer 3');
  console.assert(results[3] === 'step4', 'Wrong answer 4');
}