scroll cache module and raf loop

gistfile1.js

export default {

  scrollY: '',

  getScrollY() {
    return (window.pageYOffset !== undefined) ? window.pageYOffset : (document.documentElement || document.body.parentNode || document.body).scrollTop;
  },
  init() {
    window.addEventListener('scroll', (e) => {
      this.scrollY = this.getScrollY();
    });
    this.scrollY = this.getScrollY();
  }
}


function componentInViewport(ts) {

      let rootNode = self.getDOMNode();

      if(isOnScreen(rootNode, 600)) {
        self.setState({
          componentInViewport: true
        });
        if (self.onComponentInViewport) {
          self.onComponentInViewport();
        }
        window.cancelAnimationFrame(self.animationFrameId);
      } else {
        self.animationFrameId = window.requestAnimationFrame(componentInViewport);
      }

    }

    this.animationFrameId = window.requestAnimationFrame(componentInViewport);