var elem = document.getElementById("animatedElem"),
  left = 0,
  lastFrame = +new Date,
  timer;
// Move the element on the right at ~600px/s
timer = setInterval(function() {
  var now = +new Date,
    deltaT = now - lastFrame;
  elem.style.left = ( left += 10 * deltaT / 16 ) + "px";
  lastFrame = now;
  // clear the timer at 400px to stop the animation
  if ( left > 400 ) {
    clearInterval( timer );
  }
}, 16);