javascript job queue

queue.js

module.exports = Queue;

function Queue(action, concurrency) {
  this.action = action;
  this.concurrency = concurrency || 1;

  this.waiting = [];
  this.running = 0;
}

Queue.prototype.push = function(data, cb) {
  this.waiting.push({data: data, cb: cb});
  this.run();

  return this;
};

Queue.prototype.run = function() {
  for (var i=this.running;i<this.concurrency;++i) {
    var job = this.waiting.shift();

    if (!job) { break; }

    this.running++;
    this.action(job.data, this.wrap(job.data, job.cb));
  }

  return this;
};

Queue.prototype.wrap = function(job, cb) {
  var self = this;
  return function() {
    self.running--;
    self.run();
    cb.apply(job.data, arguments);
  };
};