callback.js

var img = new Image();

setup = function() {
  var body = document.getElementById('body');
  var canvas = document.createElement('canvas');
  var ctx = canvas.getContext('2d');
	
  canvas.width = window.innerWidth;
  canvas.height = window.innerHeight;

  body.appendChild(canvas);

  img.onload = onImageLoad;
  img.src    = "/media/img/gamedev/ralphyrobot.png";
    
  body.appendChild(img);
};

onImageLoad = function(){
  console.log("Image Loaded");
};