I want callbacks

gistfile1.js

var vi = new versalInterface();

var Gadget = function() {
  var createListeners = function() {
    vi.on('attached', this.render());
    
    // I just want to set a general re-render listener when config changes
    vi.on('attributesChanged', function(data) {
      for (var key in data) {
        this.config[key] = data[key];
      }
      
      // here I have to special case in the event that I get an image
      if (data.asset) {
        document.body.innerHTML += /* picture markup */;
      }
      
      this.render();
    }.bind(this));
  }
  
  this.render = function() {
    var gadgetHtml = '';
    document.body.innerHTML = '';
    
    gadgetHtml = '<button class="upload">upload</button>';
    document.body.innerHTML = gadgetHtml;
    
    document.querySelector('upload').addEventListener('click', function(e) {
      e.preventDefault();
      
      vi.trigger('requestAsset', { /* ... */ }, /* why can't I put a callback here */);
    })
    
    return this;
  }
};

Because it will be handled by vi.on('attributesChanged', function(){})