var start = performance.now();
var box = document.querySelector('.to-animate');
var path = document.querySelector('path');
var len = path.getTotalLength();

function frame() {
  var now = performance.now();
  var phase = ((now - start) / 6000) % 1;
  var point = path.getPointAtLength(len * phase);
  box.style.transform = 'translate3d(' + point.x + 'px,' + point.y + 'px,0)';
  requestAnimationFrame(frame);
}

frame();