Collision Detection

$(document).ready(function() {
 
    //define canvas
    var canvasElement = document.getElementById('canvas');
    var canvas = canvasElement.getContext("2d");
 
    //define objects
    var box = spritify({ movement : false, animation : false, image : 'box.png', posY : 184, posX : 184 });
    var character = spritify({ collisionObjs : 'collisionObjs' });
 
    //define collision objects
    window.collisionObjs = new Array();
    window.collisionObjs[0] = box;
 
    function draw() {
      canvas.clearRect(0, 0, 400, 400);
      canvas.fillStyle = "green";
      canvas.fillRect(0, 0, 400, 400);
 
      //draw/update character
      character.spritifyObj.update();
      character.spritifyObj.draw();
 
      //draw/update collisionObjs
      if (window.collisionObjs) {
        for(var x = 0; x < window.collisionObjs.length; x++) {
          window.collisionObjs[x].spritifyObj.update();
          window.collisionObjs[x].spritifyObj.draw();
        }
      }
 
    }
 
    setInterval(function() {
      draw();
    }, 1000/30);
 
  });