Update Dispatcher.js

[volkanunsal]

I think Array.filter expects a boolean return value –– am I correct in assuming the callback function should be written like this?

(First time submitting a pull request on this repo.)

[vjeux]

cc @fisherwebdev

[fisherwebdev]

Thanks for catching this.

Style nits: please expand the anonymous function to three lines instead of putting it all on one line. Also please add the semicolon at the end.

var selectedPromises = _promises.filter(function(/*object*/ _, /*number*/ j) {
  return promiseIndexes.indexOf(j) !== -1;
});

[volkanunsal]

Done and done done!