var photos = new Array();
var currPhoto = 0;

function setPhoto(idx){
  var img = document.getElementById("photo");
  img.src = "img/photo/" + photos[idx] + ".jpg";
  currPhoto = idx;
  return;
}

function nextPhoto() {
  if (((currPhoto * 1)+1) < photos.length) {
    setPhoto(currPhoto +1);
  } else {
    setPhoto(0);
  }
}

function prevPhoto() {
  if (((currPhoto * 1) - 1) < 0) {
    setPhoto(photos.length -1);
  } else {
    setPhoto((currPhoto * 1) - 1);
  }
}