WorkCrew - a WebWorker work queue library

workcrew.js

/*
WorkCrew - a WebWorker work queue library

Usage:

  // Create an 8 worker pool using worker.js.
  var crew = new WorkCrew('worker.js', 8);

  // Do something whenever a job is completed.
  // The result object structure is
  // {
  //   id: work unit ID,
  //   result: message received from worker 
  // }
  crew.oncomplete = function(result) {
    console.log(result.id, result.result);
  };

  // Add some work to the queue.
  // The work unit is postMessaged to one of
  // the workers.
  var workId = crew.addWork(myWorkUnit);

  // Add an onfinish event handler.
  // Fired when the queue is empty and all workers
  // are free.
  crew.onfinish = function() {
    console.log('All work in queue finished!');
  };

*/
WorkCrew = function(filename, count) {
  this.filename = filename;
  this.count = count || 4;
  this.queue = [];
  this.results = [];
  this.pool = [];
  this.working = {};
  this.uuid = 0;
  this.fillPool();
};

WorkCrew.prototype.onfinish = function() {};

WorkCrew.prototype.oncomplete = function(res) {
  return [res.id, res.result];
};

WorkCrew.prototype.addWork = function(work) {
  var id = this.uuid++;
  this.queue.push({id: id, work: work});
  this.processQueue();
  return id;
};

WorkCrew.prototype.processQueue = function() {
  if (this.queue.length == 0 && this.pool.length == this.count) {
    if (this.onfinish)
      this.onfinish();
  } else {
    while (this.queue.length > 0 && this.pool.length > 0) {
      var unit = this.queue.shift();
      var worker = this.pool.shift();
      worker.id = unit.id;
      this.working[worker.id] = worker;
      worker.postMessage(unit.work);
    }
  }
};

WorkCrew.prototype.addWorker = function() {
  var w = new Worker(this.filename);
  var self = this;
  w.onmessage = function(res) {
    var id = this.id;
    delete self.working[this.id];
    this.id = null;
    self.pool.push(this);
    try {
      self.oncomplete({id: id, result: res});
    } catch(e) {
      console.log(e);
    }
    self.processQueue();
  };
  this.pool.push(w);
};

WorkCrew.prototype.fillPool = function() {
  for (var i=0; i<this.count; i++) {
    this.addWorker();
  }
};

Given that this would have to run on the main UI thread, wouldn't the while loop block the UI until all work is processed? I tried to implement this in a worker itself, but it seems like Chrome doesn't support creating workers from worker threads.

The time spent within the while loop is minimal and limited by the time it takes to serve your workers (this.pool.length) with tasks.

The returning workers as well as incoming tasks will trigger the processQueue() method again.

I'm getting DataCloneError on IE11. thanks!

working does nothing : )