var resources = document.querySelector('#resources'),
    log = document.querySelector('#log'),
    time = 0;

document.addEventListener('keydown', keydown, false);
document.addEventListener('keyup', keyup, false);

function keydown(ev) {
  if (time === 0) { 
    time = ev.timeStamp; 
    log.classList.add('animate');
  }
}
function keyup(ev) {
  if (time !== 0) {
    log.innerHTML = ev.timeStamp - time;
    time = 0;
    log.classList.remove('animate');
  }
}