Abusing JavaScript generators and yield one can create task schedulers that essentially allow to write code that waits without blocking for asynchronous events. Originally http://lists.w3.org/Archives/Public/www-archive/2008Jul/0009.html and http://lists.w3.org/Archives/Public/www-archive/2013Apr/0043.html The difference between the two versions…

waiting-for-dom-events-using-yield-2008.js

  function OnYieldWaitForEvent(cor, target, name, phase) {
    var self = arguments.callee;
    target.addEventListener(name, function(evt) {

      // We need to unregister the listener to save resources
      // and to avoid getting called if the event occurs again
      evt.currentTarget.removeEventListener(name, self, phase);

      // Resume the waiting function
      cor.next();
    }, phase);
  };

  function ExecWithOnYield(func) {
    var generator = new func;
    generator.next();

    // There is no arguments.generator or `this generator` yet
    // and arguments.callee refers to the Function object, so
    // we have to pass a self-reference to the instance.
    generator.send(generator);
  };

  function test() {
    var self = yield;

    // Create a new <img> object
    var img1 = new Image(315, 48);

    OnYieldWaitForEvent(self, img1, 'load', false);
    img1.src = 'http://www.w3.org/Icons/w3c_main';
    yield; // wait for img1 'load'

    // ... load more images here ...

    // Now draw them all on a <canvas>

    // Signal we are done so the event handler does not have to
    // catch an exception that would otherwise be generated.
    yield 'done';
  };

  ExecWithOnYield(test);

waiting-for-dom-events-using-yield-2013.js

  function OnYieldWaitForEvent(target, name, useCapture) {
    return function(resume) {
      var listener;
      listener = function(){
        target.removeEventListener(name, listener, useCapture);
        resume();
      };
      target.addEventListener(name, listener, useCapture);
    }
  }
  
  function ExecWithOnYield(func) {
    var generator = new func;
    var ExecOneStep;
    ExecOneStep = function(){
      try {
        var wrapped = generator.next();
        // TODO: what if `wrapped` throws `StopIteration`?
        wrapped(ExecOneStep);
      }
      catch (e) {
        if (e instanceof StopIteration) {
          console.log("StopIteration");
        } else {
          console.log("other exception");
        }
      }
    }
    ExecOneStep(generator);
  };
  
  function test() {
  
    var img1 = new Image(315, 48);
    img1.src = 'http://www.w3.org/Icons/w3c_main';
    yield OnYieldWaitForEvent(img1, 'load', false);
  
    console.log("img1 has loaded when we get here");
  };
  
  ExecWithOnYield(test);

With all the addEventListener, and removeEventListener would this cause issues for a ton of events? Like if you were to do mouse move tracking in a loop?

Using it for clicks would probably be ok.