Has scroll collision; returns Boolean is target touches viewable scroll

has_scroll_collision.js

((target)=>{
  function getPos(el){
    for (var lx=0, ly=0;
      el != null;
      lx += el.offsetLeft, ly += el.offsetTop, el = el.offsetParent);
    return {x: lx,y: ly};     
  }

  function getScrollAmount(){
    const doc = document.documentElement;

    return {
      left: (window.pageXOffset || doc.scrollLeft) - (doc.clientLeft || 0),
      top: (window.pageYOffset || doc.scrollTop)  - (doc.clientTop || 0)
    };
  }

  function getScrollMax(){
    const scrollAmount = getScrollAmount();

    return {
      right: window.innerWidth + scrollAmount.left,
      bottom: window.innerHeight + getScrollAmount().top
    };
  }

  function hasScrollCollision(el){
    const pos = getPos(el),
          scroll = getScrollMax();

    return scroll.right >= pos.x &&
           scroll.bottom >= pos.y;
  }

  return hasScrollCollision(target);
})(document.querySelector("body>div.container"));