web worker as a promise

webworker-as-promise.js

// Usage
var workerFibo = createPromiseWorker(function(x){
  return (function fibo(n){
    if (n > 1) {
      return fibo(n - 1) + fibo(n - 2);
    } else {
      return 1;
    }
  })(x)
});

Promise.all([0, 1, 2, 3, 5, 8, 13, 21, 34].map(workerFibo)).then(console.log);


// Module
var Worker = require('webworker-threads').Worker;
var Promise = require('promise');
var fnRegex = require('function-regex');
function toArray (arr) { return Array.prototype.slice.call(arr) }
function parseFunction(fn) {
  if (typeof fn === 'function') {
    fn = fn.toString();
  }
  var match = fnRegex().exec(fn);

  var _parameters = match[2] || '';
  var _arguments = _parameters.length && _parameters.replace(/\s/g, '').split(',') || [];

  return {
    name: match[1] || 'anonymous',
    arguments: _arguments,
    body: match[3] || ''
  };
};

module.exports = function createPromiseWorker(compute) {
  var i = 0;
  var parsedCompute = parseFunction(compute);
  var promises = [];

  var worker = new Worker(function () {
    onmessage = function (e) {
      var fn = e.data.method;

      var method = Function.apply(null, fn.arguments.concat(fn.body))

      try {
        var results = method.apply(null, e.data.arguments);

        postMessage({
          type: 'success',
          data: results,
          id: e.data.id
        });
      } catch (err) {
        postMessage({
          type: 'fail',
          data: err,
          id: e.data.id
        });
      }
      // this.close()
    }
  });

  worker.addEventListener('message', function (e) {
    (e.data.type === 'success'
        ? promises[e.data.id].resolve
        : promises[e.data.id].reject
    )(e.data.data);
  }, false);

  return function(){
    var args = toArray(arguments);

    return new Promise(function(resolve, reject){
      var id = i++;
      promises[id] = {resolve: resolve, reject: reject};

      worker.postMessage({
        method: parsedCompute,
        arguments: args,
        id: id
      });
    });
  }
}

/* read
* http://www.html5rocks.com/en/tutorials/workers/basics/
* http://developerblog.redhat.com/2014/05/20/communicating-large-objects-with-web-workers-in-javascript/
*
* function decompilation
* http://perfectionkills.com/state-of-function-decompilation-in-javascript/
* http://stackoverflow.com/questions/3179861/javascript-get-function-body
* */