imagesCached = false;

function swap_img(img, action) {
  if (imagesCached) {
     eval('img.src = ' + action + '.src;');
  }
}

function cacheImages() {

  for (i=0; i < cachedImages.length; i++) {
    name = cachedImages[i][0];
    name_act =  name + '_act';
    name_pass = name + '_pass';

    eval(name_pass + ' = new Image();')
    eval(name_pass + '.src = "' + cachedImages[i][1] + '";')
    eval(name_act + ' = new Image();')
    eval(name_act + '.src = "' + cachedImages[i][2] + '";')
  }
  
  imagesCached = true;
}