message: Checked window exists for isomorphic
diff: @@ -12,7 +12,7 @@ class Motion<T> extends React.Component<MotionProps<T>, any> {
  progress: 0,
  }
  static getDerivedStateFromProps(props, {items: prevItems}) {
  - var tick = typeof window.performance !== 'undefined' ? window.performance.now() : 0;
  + var tick = typeof window !== 'undefined' && window.performance ? window.performance.now() : 0;
  var {items, moving} = Motion.move(tick, prevItems, props);
  return {items, restart: moving};
  }
  